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United States Patent |
6,207,266
|
Kanbara
,   et al.
|
March 27, 2001
|
Electromagnetically shielding bonding film
Abstract
Provided is bonding film in the form of web which has a high
electromagnetic shielding effect for electromagnetic radiation from the
front surface of a display device, and other favorable properties such as
an infrared blocking property, a transparency, a invisibility and a
favorable bonding property. The bonding film typically includes base film,
a geometrically patterned electroconductive layer placed over the base
film so as to achieve an aperture ratio of 80% of more, and a bonding
layer for attaching the assembly to an object. The film may be applied to
the surface of a transparent sheet member for the convenience of handling,
and such an assembly has a symmetric structure so that the warping of the
assembly may be minimized. The bonding film may be interposed between a
pair transparent base sheets, or the bonding film may be applied over two
sides a transparent base sheet. The assembly may further include an
infrared blocking layer and an anti-glare layer.
Inventors:
|
Kanbara; Hisashige (Oyama, JP);
Nakaso; Akishi (Oyama, JP);
Tosaka; Minoru (Shimodate, JP)
|
Assignee:
|
Hitachi Chemical Company, Ltd. (Tokyo, JP)
|
Appl. No.:
|
975649 |
Filed:
|
November 21, 1997 |
Foreign Application Priority Data
| Jun 03, 1997[JP] | 9-145075 |
| Jun 03, 1997[JP] | 9-145076 |
| Jun 06, 1997[JP] | 9-149208 |
Current U.S. Class: |
428/323; 174/35R; 361/682; 422/186.02; 428/328 |
Intern'l Class: |
H05K 9/0/0 |
Field of Search: |
428/323,328
174/35 R
422/186.02
361/682
|
References Cited
Foreign Patent Documents |
62-57297 | Mar., 1987 | JP.
| |
1-170098 | Jul., 1989 | JP.
| |
1-278800 | Nov., 1989 | JP.
| |
2-52499 | Feb., 1990 | JP.
| |
3-35284 | Feb., 1991 | JP.
| |
5-269912 | Oct., 1993 | JP.
| |
5-283889 | Oct., 1993 | JP.
| |
5-323101 | Dec., 1993 | JP.
| |
5-327274 | Dec., 1993 | JP.
| |
Primary Examiner: Resan; Stevan A.
Attorney, Agent or Firm: Dickstein Shapiro Morin & Oshinsky, LLP
Claims
What we claim is:
1. A method for making an electromagnetic shielding bonding film,
comprising:
forming geometrically patterned electroconductive material having a line
width of 40 .mu.m or less, a line spacing of 200 .mu.m or more, and a line
thickness of 40 .mu.m or less over a substantially transparent base film,
the geometric pattern providing an aperture ratio of 80% or more;
coating a bonding agent composition over a part or an entirety of at least
one side of said base film, wherein a difference in the refraction index
between said transparent base film and the bonding layer formed by said
coated bonding agent is 0.14 or less;
said base film being prepared as a roll web, and at least most of said
steps are carried out in a continuous manner.
2. A method for making electromagnetic shielding bonding film according to
claim 1, further comprising the step of forming an infrared blocking layer
by using an infrared blocking composition having an absorption ratio of
50% or more for infrared light of 900 to 1,100 nm in wavelength at least
on one side of said base film.
3. A method for making electromagnetic shielding bonding film according to
claim 1, wherein said geometric patterned electroconductive material is
formed by etching.
4. A method for making electromagnetic shielding bonding film according to
claim 1, wherein said bonding agent composition has a refractive index of
1.45 to 1.60.
5. A method for making electromagnetic shielding bonding film according to
claim 4, wherein said transparent base film consists of
polyethylene-terephthalate film.
6. A method for making electromagnetic shielding bonding film according to
claim 1, wherein said infrared blocking layer is incorporated in said
coating of said bonding agent composition.
7. A method for making electromagnetic shielding bonding film according to
claim 1, wherein said geometric patterned electroconductive material layer
consists of a member selected from a group consisting of copper, aluminum
and nickel layer.
8. A method for making electromagnetic shielding bonding film according to
claim 7, wherein said geometric patterned electroconductive material has a
thickness of 3 to 40 .mu.m, and a surface of said transparent base film
carrying said electroconductive material consists of a coarse surface
having a surface roughness of 1 .mu.m or more.
9. A method for making electromagnetic shielding bonding film according to
claim 7, wherein said electroconductive material consists of copper which
has a darkened surface.
10. A method for making electromagnetic shielding bonding film according to
claim 1, wherein said electroconductive material consists of paramagnetic
metallic material.
11. A display device using electromagnetic shielding bonding film which is
made by the method according to any one of claims 1-10.
12. An electromagnetic shielding assembly incorporating electromagnetic
shielding bonding film which is made by the method according to any one of
claims 1-10.
13. A bonding film which has an optically transparent and
electromagnetically shielding property, comprising:
a substantially transparent base film;
geometrically patterned electroconductive material formed at least on one
side of said transparent base film;
a bonding layer placed at least partly on one side of said base film;
wherein said geometric patterned electroconductive material has a line
width of 40 .mu.m or less, a line spacing of 200 .mu.m or more, and a line
thickness of 40 .mu.m or less; and
a difference in refraction index between said transparent base film and
said bonding layer is 0.14 or less.
14. Bonding film which has an optically transparent and electromagnetically
shielding property according to claim 13, further comprising a bonding
agent layer interposed between said transparent base film and said bonding
layer, and differences in refraction index between said bonding agent
layer and said transparent base film, and between said bonding agent layer
and said bonding layer are 0.14 or less.
15. Bonding film which has an optically transparent and electromagnetically
shielding property according to claim 13, wherein said transparent film
consists of polyethylene-terephthalate film.
16. Bonding film which has an optically transparent and electromagnetically
shielding property according to claim 13, wherein said electroconductive
material consists of a member selected from a group consisting of copper,
aluminum or nickel.
17. Bonding film which has an optically transparent and electromagnetically
shielding property according to claim 16, wherein said electroconductive
material has a thickness of 3 to 40 .mu.m, and a surface thereof bonded to
said transparent film consists of a coarse surface.
18. Bonding film which has an optically transparent and electromagnetically
shielding property according to claim 13, wherein said electroconductive
material consists of copper which having a darkened surface.
19. Bonding film which has an optically transparent and electromagnetically
shielding property according to claim 13, wherein said electroconductive
material layer is geometrically patterned by a chemical etching process.
20. Bonding film which has an optically transparent and electromagnetically
shielding property according to claim 13, wherein said electroconductive
material consists of paramagnetic metallic material.
21. Bonding film which has an optically transparent and electromagnetically
shielding property according to claim 13, wherein said bonding film is
incorporated with an infrared blocking layer which has an overall infrared
absorption ratio of 50% or more in a wavelength range of 900 to 1,100 nm.
22. A display device using the bonding film which has an optically
transparent and electromagnetically shielding property according to any
one of claims 13 to 21.
23. An electromagnetic shielding assembly using the bonding film which has
an optically transparent and electromagnetically shielding property
according to any one of claims 13 to 21.
24. An electromagnetic shielding assembly, comprising:
electromagnetic shielding film, wherein said electromagnetic shielding film
comprises substantially transparent plastic base film, and geometrically
patterned electroconductive material formed at least on one side of said
transparent base film, said geometrically patterned material having a line
width of 40 .mu.m or less, a line spacing of 200 .mu.m or more, and a line
thickness of 40 .mu.m or less; and
a pair of substantially transparent base sheets attached to either side of
said transparent plastic film, said base sheets having a substantially
identical thickness, and wherein a difference in the refraction index
between said transparent base sheet and said transparent base film is 0.14
or less.
25. An electromagnetic shielding assembly according to claim 24, wherein
said geometric patterned electroconductive material has a line width of 25
.mu.m or less, a line spacing of 500 .mu.m or more, and a line thickness
of 18 .mu.m or less.
26. An electromagnetic shielding assembly according to claim 24, wherein
said transparent base film consists of polyethylene-terephthalate film.
27. An electromagnetic shielding assembly according to claim 26, wherein
said electroconductive material has a thickness of 3 to 18 .mu.m, and a
surface thereof bonded to said transparent base film consists of a coarse
surface.
28. An electromagnetic shielding assembly according to claim 26, wherein
said electroconductive material consists of copper which at least has a
darkened surface.
29. An electromagnetic shielding assembly according to claim 24, wherein
said electroconductive material consists of a member selected from a group
consisting of copper, aluminum and nickel.
30. An electromagnetic shielding assembly according to claim 24, wherein
said electroconductive material is geometrically patterned on said
transparent base film by a chemical etching process.
31. An electromagnetic shielding assembly according to claim 24, wherein
said electroconductive material consists of paramagnetic metallic
material.
32. An electromagnetic shielding assembly according to claim 24, further
comprising a bonding layer formed at least partly at least on one side of
said electromagnetic shielding film.
33. An electromagnetic shielding assembly according to claim 24, wherein
said transparent base sheets are made of polymethylmethacrylate (PMMA).
34. A display device using the electromagnetic shielding assembly according
to any one of claims 24-33.
35. An electromagnetic shielding assembly, comprising:
a substantially transparent base sheet;
substantially transparent base film placed on each side of said base sheet;
said base film placed at least on one side of said base sheet consisting of
electromagnetic shielding film, wherein said electromagnetic shielding
film comprises geometrically patterned electroconductive material having a
line width of 40 .mu.m or less, a line spacing of 200 .mu.m or more, and a
line thickness of 40 .mu.m or less; and
a bonding layer for attaching a pair of mutually adjoining members, wherein
the difference in the refraction index between said transparent base sheet
and said transparent base film 0.14 or less.
36. An electromagnetic shielding assembly according to claim 35, wherein
said geometric patterned electroconductive material has a line width of 25
.mu.m or less, a line spacing of 500 .mu.m or more, and a line thickness
of 18 .mu.m or less.
37. An electromagnetic shielding assembly according to claim 35, wherein
said electroconductive material consists of a member selected from a group
consisting of copper, aluminum and nickel.
38. An electromagnetic shielding assembly according to claim 37, wherein
said electroconductive material has a thickness of 3 to 18 .mu.m, and a
surface thereof bonded to said transparent base film consists of a coarse
surface.
39. An electromagnetic shielding assembly according to claim 37, wherein
said electroconductive material consists of copper which has a darkened
surface.
40. An electromagnetic shielding assembly according to claim 35, wherein
said electroconductive material is geometrically patterned on said
transparent base film by a chemical etching process.
41. An electromagnetic shielding assembly according to claim 35, wherein
said electroconductive material consists of paramagnetic metallic
material.
42. An electromagnetic shielding assembly according to claim 35, wherein
said base film placed at least on one side of said base sheet comprises an
anti-glare or anti-reflective layer.
43. An electromagnetic shielding assembly according to claim 35, wherein
said base film placed at least on one side of said base sheet comprises an
infrared blocking layer.
44. An electromagnetic shielding assembly according to claim 35, wherein
said base film is placed over the two sides of said transparent base sheet
by a roll laminating method.
45. An electromagnetic shielding assembly according to claim 35, wherein
said transparent base film consists of polyethylene-terephthalate film.
46. An electromagnetic shielding assembly according to claim 35, wherein
said transparent base sheet is made of polymethylmethacrylate (PMMA).
47. A display device using the electromagnetic shielding assembly according
to any one of claims 35-46.
48. A method for making an electromagnetic shielding bonding film,
comprising:
forming geometrically patterned electroconductive material having a line
width of 40 .mu.m or less, a line spacing of 200 .mu.m or more, and a line
thickness of 40 .mu.m or less over a substantially transparent base film,
the geometric pattern providing an aperture ratio of 80% or more, wherein
said transparent base film is at least one member selected from the group
consisting of polyesters, polyolefins, vinyl resins, polysulfone,
polyethersulfone, polycarbonate, polyamide, polyimide and acrylic resins
having a visible light transmission factor of 70% or more;
coating a bonding agent composition over a part or an entirety of at least
one side of said base film, wherein a difference in the refraction index
between said transparent base film and the bonding layer formed by said
coated bonding agent is 0.14 or less;
said base film being prepared as a roll web.
49. A method for making electromagnetic shielding bonding film according to
claim 48, wherein said transparent base film is at least one member
selected from the group consisting of polyethylene terephthalate (PET),
polyethylene napthalate, polyethylene, polypropylene, polystyrene, EVA,
polyvinyl chloride and polyvinylidene chloride.
50. A method for making electromagnetic shielding bonding film according to
claim 49, wherein said transparent base film is at least one member
selected from the group consisting of polyethylene terephthalate (PET),
polyethylene napthalate, and polyethylene.
51. A method for making electromagnetic shielding bonding film according to
claim 50, wherein said transparent base film does not contain a filler.
52. A method for making electromagnetic shielding bonding film according to
claim 50, wherein at least most of said steps are carried out in a
continuous manner.
Description
TECHNICAL FIELD
The present invention relates to a method for making electromagnetic
shielding bonding film for shielding electromagnetic radiation which may
be produced from the front surfaces of CRT, PDP (plasma display panel),
liquid crystal, EL and other display devices. The present invention also
relates to bonding film which is capable of shielding electromagnetic
radiation from the front surface of such display devices as CRT, PDP
(plasma display), LCD, and EL, and a display device and an electromagnetic
shielding assembly using such film.
BACKGROUND OF THE INVENTION
Recently, with the increase in the use of various electric and electronic
appliances, problems of electromagnetic noises or interferences (EMI) have
been on the increase. Such noises may be generally classified into
conduction noises and emission or radiation noises. The use of noise
filters is a typical measure against conduction noises. As for radiation
noises, it is necessary to electromagnetically insulate a prescribed
space. To this end, the appliance may be enclosed in a metallic or
otherwise electroconductive casing, a metallic plate may be placed between
the two circuit boards, or metallic foil may be wrapped around the cable.
These measures may provide an adequate electromagnetic shield for the
circuit or the power source block, but are unsuitable for shielding
electromagnetic radiation which may be produced from the front surface of
a display device such as a CRT or a PDP because such measures require an
opaque material layer to be placed in front of the display device.
Methods for providing both an electromagnetic shielding effect and a
transparency have been previously proposed (see Japanese patent laid open
publications Nos. 1-278800 and 5-323101) which are based on forming
electroconductive thin film over the surface of a transparent base member
by vapor depositing metal or metal oxide.
There have also been proposed electromagnetic shielding materials having
highly electroconductive fibers embedded in a transparent base material
layer (see Japanese patent laid open publications Nos. 5-327274 and
5-269912), electromagnetic shielding materials having electroconductive
resin material containing metallic powder or the like directly deposited
or printed on a transparent base board (see Japanese patent laid open
publications Nos. 62-57297 and 2-52499), and an electromagnetic shielding
material having a transparent resin layer formed over a transparent base
board such as polycarbonate board having the thickness of approximately 2
mm, and a copper layer of a mesh pattern formed over the resin layer by
electroless plating (see Japanese patent laid open publication No.
5-283889).
According to the methods of forming a thin electroconductive layer by vapor
depositing metal or metal oxide onto a transparent base board which were
proposed in Japanese patent laid open publications Nos. 1-278800 and
4-323101 and purported to achieve both an electromagnetic shielding
capability and a transparency, if the thickness of the electroconductive
layer is reduced to a sufficient level (a few hundred .ANG. to 2,000
.ANG.), the surface resistance of the electroconductive layer becomes so
large than the shielding effect for the frequency range of 1 MHz to 1 GHz
will be less than 20 dB which is significantly lower than the required
level of 30 dB or more.
As for the electromagnetic shielding material consisting of a transparent
base member having electroconductive fibers embedded therein such as those
proposed in Japanese patent laid open publications Nos. 5-327274 and
5-269912, a sufficiently high electromagnetic shielding effect of 40 to 50
dB can be achieved for the frequency range of 1 MHz to 1 GHz, but the
fiber diameter which is required for regularly arranging the
electroconductive fibers so as to achieve such a shielding effect becomes
as large as 35 .mu.m, and the fibers are so visible (which is referred to
as "visibility" hereinafter) that the shielding material is quite unfit
for application to display devices. In the case of the electromagnetic
shielding material made by directly printing electroconductive ink
containing metallic powder or the like on a transparent base board,
similarly, the line width is no less than 100 .mu.m due to the limitation
of printing precision so that the visibility makes the material
unsuitable. As for the shielding material formed by forming a transparent
resin layer over a transparent base board made of a polycarbonate plate or
the like having a thickness in the order of 2 mm, and forming a copper
mesh pattern thereon by electroless plating, the surface of the
transparent base board is required to be roughened or made coarse so as to
achieve a sufficient adhesive power for the electroless plating. This
roughening process requires the use of toxic oxidants such as chromic acid
and permanganate acid, and can produce a desired result only when the base
board is made of ABS resin. According to this method, even when an
electromagnetic shielding effect and a transparency are both achieved, the
thickness of the transparent base board cannot be reduced to a sufficient
level so that the material is not suited to be formed into a sufficiently
thin film or web. If the transparent base board has a significant
thickness, as it cannot be closely attached to the surface of the display
device, there will be a leakage of electromagnetic radiation. Also, in
regard to the manufacturing process, because the shielding material cannot
be put into the form of rolls, the material tends to be undesirably bulky
and the unsuitability of the material to automation causes an increase in
the production cost.
The electromagnetic radiation from the front surface of the display device
that needs to be shielded is not limited the electromagnetic radiation in
the frequency range of 1 MHz to 1 GHz that has to be reduced by 30 dB or
more, but the infrared radiation in the wavelength range of 900 to 1,100
nm is also required to be blocked as it interferes with VTR equipment.
In addition to a favorable transparency for visible light, the material is
required to have a favorable bonding property which allows it to be
closely attached to the display surface so as to effectively shut off
electromagnetic radiation, and to achieve a invisibility which makes the
presence of the shielding material unnoticeable to the viewer. The bonding
property includes the capability of the material to be attached to the
surface of any one of a number of widely used polymer plate materials as
well as to the surface of glass at a relatively low temperature, and to
continue to maintain the close contact with the material over extended
periods of time. However, such desirable material that can be formed into
web or a roll, and which can sufficiently meet the requirements of the
electromagnetic shielding effect, the infrared radiation blocking effect,
the transparency, the invisibility, and the bonding property has not been
hitherto available.
The part of the surface of the transparent plastic base member from which
the electroconductive material has been removed presents an irregular
surface because the surface was deliberately formed into an irregular
surface in order to increase the adhesion force or because the marks of
the reverse surface of the electroconductive material were imprinted on
the surface of the transparent plastic base member. Therefore, the
irregular reflection on the surface may damage the transparency of the
base member, but by evenly applying a resin material layer, having a
refraction index close to that of the base member, over such an irregular
surface, the irregular reflection is minimized so that the transparency of
the base member may be restored. The electroconductive material
geometrically patterned on the surface of the transparent plastic base
member has such a fine line width that it is practically invisible to
naked eyes. The large line spacing also contributes to the invisibility of
the electroconductive material.
Also, it is believed that, because the pitch of the geometric pattern is
sufficiently smaller than the wavelength of the electromagnetic radiation
that is desired to be shielded, a superior shielding performance can be
achieved.
Also, the PDP panel, which is one type of flat panel, requires its front
surface to be free from any warping. To control such a warping, it is
preferable to use a symmetric structure, and is conceivable to attach a
pair of transparent plastic sheets onto either side of a bonding agent
layer. However, because the front panel of a display device is normally
required to have a thickness of 2 to 5 mm in view of the possibility of
breaking the glass and the ease of handling, a pressing process is
necessary in view of the thermal conduction to the bonding agent in order
to produce such an assembly. Additionally, the front panel of the display
requires an anti-glare processing or an anti-reflection processing, it is
required to be carried out directly on the transparent plastic base sheet,
and the production process must be carried out as a batch process. For
these two reasons, the production of such an assembly involves the problem
that a continuous production process is not possible, and hence the
production cost would be undesirably high.
BRIEF SUMMARY OF THE INVENTION
In view of such problems of the prior art, a primary object of the present
invention is to provide electromagnetic shielding bonding film which may
be applied to a member or an area where electromagnetic shielding and
optical transparency are both required.
A second object of the present invention is to provide electromagnetic
shielding bonding film which is easy to handle and economical to
manufacture.
A third object of the present invention is to provide electromagnetic
shielding bonding film which has a favorable optical properties such as
high visible light transparency, invisibility of electroconductive
shielding material, and freedom front image distortion.
A fourth object of the present invention is to provide electromagnetic
shielding bonding film which can be conveniently applied to a wide range
of display devices and electromagnetic shielding assemblies.
A fifth object of the present invention is to provide an electromagnetic
shielding assembly incorporating such electromagnetic shielding bonding
film which is highly effective in shutting off electromagnetic radiation
but highly transparent to visible light.
A sixth object of the present invention is to provide an electromagnetic
shielding assembly which is capable of blocking infrared radiation as
well.
A seventh object of the present invention is to provide an electromagnetic
shielding assembly which is capable of controlling spurious reflection and
glare on the surface of the assembly.
According to the present invention, these and other objects can be
accomplished by providing a method for making electromagnetic shielding
bonding film, comprising the steps of: forming geometrically patterned
electroconductive material over substantially transparent base film, the
geometric pattern providing an aperture ratio of 80% of more; coating a
bonding agent composition over a part of an entirety of at least one side
of the base film, the bonding agent composition having a refractive index
similar to that of the base film; the base film being prepared as a roll
web, and at least most of the steps are carried out in a continuous
manner.
Thus, bonding film having a favorable electromagnetic shielding capability
and a high visible light transparency can be produced in an efficient and
economical manner. The production process may further comprise the step of
forming an infrared blocking layer by using an infrared blocking
composition having an absorption ratio of 50% or more for infrared light
of 900 to 1,100 nm in wavelength at least on one side of the base film,
and this process can also be implemented a a substantially continuous
operation.
The geometric patterned electroconductive material may be formed in an
economical and precise manner by etching. To achieve a favorable
transparency of the produced bonding film, the bonding agent composition
should have a refractive index of 1.45 to 1.60 which is similar to that of
most widely used plastic or otherwise transparent material suitable for
base film such as polyethylene-terephthalate. To the end of reducing the
number of production steps, and simplify the structure of the bonding
film, the infrared blocking layer may be incorporated in the coating of
the bonding agent composition.
To achieve a desired electromagnetic shielding performance without
impairing the visible light transparency and the view angle, the geometric
patterned electroconductive material may have a line width 40 .mu.m or
less, a line spacing of 200 .mu.m or more, and a line thickness of 40
.mu.m or less. Preferably, the geometric patterned electroconductive
material layer consists of a member selected from a group consisting of
copper, aluminum and nickel layer, and the geometric patterned
electroconductive material has a thickness of 3 to 40 .mu.m. To achieve a
favorable attachment between the electroconductive material and the base
film, a surface of the transparent base film carrying the
electroconductive material and/or the reverse surface of the
electroconductive material layer may consist of a coarse surface having a
surface roughness of 1 .mu.m or or. To achieve a favorable electromagnetic
shielding performance and a high contrast image transmission, the
electroconductive material may consist of copper which has a darkened
surface. To the end of even more effectively shielding a magnetic field,
the electroconductive material may consist of paramagnetic metallic
material.
The present invention provides bonding film which has a highly optically
transparent and electromagnetically shielding property, by combining
substantially transparent base film; geometrically patterned
electroconductive material formed at least on one side of the transparent
base film; a bonding layer placed at least partly at least on one side of
the base film; wherein the geometric patterned electroconductive material
has a line width of 40 .mu.m or less, a line spacing of 200 .mu.m or more,
and a line thickness of 40 .mu.m or less; and a difference in refraction
index between the transparent base film and the bonding layer is 0.14 or
less. When a bonding agent layer is interposed between the transparent
base film and the bonding layer, and differences in refraction index
between the bonding agent layer and the transparent base film, and between
the bonding agent layer and the bonding layer should be 0.14 or less so
that a desired transparency may be achieved.
The present invention additionally provides an electromagnetic shielding
assembly, comprising: electromagnetic shielding film; and a pair of
substantially transparent base sheets attached to either side of the
transparent plastic film, the plastic base sheets having a substantially
identical thickness. This assembly is particularly suitable for use on the
front surface of a display device. In particular, because of the
symmetrically laminated arrangement, the assembly is free from any
warping. Alternatively, the electromagnetic shielding assembly may
comprise a substantially transparent base sheet; substantially transparent
base film placed on each side of the base sheet; the base film placed at
least on one side of the base sheet consisting of electromagnetic
shielding film. The transparent base sheet is preferably made of
polymethylmethacrylate (PMMA). In such assemblies also, by controlling the
difference between adjoining transparent members such as base sheet, base
film, and bonding layers so as to be at least less than 0.14, it is
possible to achieve a favorable visible light transparency.
When producing such assemblies, the temperature at which the lamination
process should be carried out may be selected by taking into account Tg
and the crosslinking/curing temperature of the bonding agent layer, and Tg
of the transparent plastic base sheet. The temperature range of
100.degree. C. to 300.degree. C. is preferred. If the temperature is too
low, the bonding may become insufficient. If the temperature is too high,
the bonding agent may seep out, and the transparent plastic base sheet may
deform.
The assembly of the present invention may be mounted on the front surface
of a display device, or mounted on the cases for measuring instruments,
measuring devices and manufacturing devices, and inspection windows for
such cases as well as for protecting appliances and devices from
electromagnetic radiation by being mounted on the cases for such
appliances and devices, and windows for such cases that require to be
transparent.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now the present invention is described in the following in more detail.
The plastic film as used in this application includes those made of
polyesters such as polyethylene terephthalate (PET) and polyethylene
naphthalate, polyolefins such as polyethylene, polypropylene, polystyrene
and EVA, vinyl resins such as polyvinyl chloride and polyvinylidene
chloride, polysulfone, polyethersulfone, polycarbonate, polyamide,
polyimide, and acrylic resins which have a transmission factor of 70% or
more for visible light. These materials may be used as a single layer or
multi layers combining two or more layers. In view of transparency,
heat-resistance, handling and cost, polyethylene terephthalate is
particularly suitable. The thickness of the base material is preferably in
the range of 5 to 200 .mu.m. If the thickness is less than 5 .mu.m, the
handling is impaired. If the thickness is greater than 200 .mu.m, the
transmission factor of visible light diminishes. The thickness range of 10
to 100 .mu.m is particularly preferable, and the thickness range of 25 to
50 .mu.m is even more preferable.
The electroconductive metallic material as used in this application
includes a material or an alloy of two or more selected from a group
consisting of copper, aluminum, nickel, iron, gold, silver, stainless
steel, tungsten, chromium and titanium or a combination thereof. In view
of electroconductivity, suitability for circuit fabrication and cost,
copper, aluminum and nickel are particularly suitable. The material
preferably should be in the form of metallic foil having a thickness of 3
to 40 .mu.m. If the thickness exceeds 40 .mu.m, forming the fine lines
becomes difficult, and the visible angle is reduced. If the thickness
falls below 3 .mu.m, the surface resistance increases to such an extent
that the electromagnetic shielding effect may become inadequate. It is
preferable if the electroconductive metallic material consists of copper
having at least its surface darkened because a high contrast can be
achieved. Also, the oxidation and fading of the electroconductive metallic
material over time can be avoided. The darkening process can be carried
outer either before or after the process of forming the geometric pattern,
but is normally carried out after forming the geometric pattern in the
manner well known in the art of printed circuit boards. For instance, the
darkening process may consist of processing the metallic material in a
water solution of sodium chlorite (31 g/liter), sodium hydroxide (15
g/liter), and trisodium phosphate (12 g/liter) for 2 minute at 95.degree.
C. It is desirable if the electroconductive metallic material consists of
paramagnetic metal as it improves the magnetic shielding effect in
addition to the shielding effect against an electric field.
Such electroconductive metallic material can be most easily brought into
close contact with plastic film of the above described type by coating a
bonding agent essentially consisting of acrylic or epoxy resin onto the
electroconductive metallic material in the form of foil or the plastic
film, and bonding these two material layers together via the bonding
agent. When the thickness of the layer of the electroconductive metallic
material is desired to be reduced, it can be achieved by one or a
combination of two or more of the thin film forming methods selected from
a group consisting of vacuum deposition, sputtering, ion plating, chemical
vapor deposition, and electroless and electric plating. The film thickness
of the electroconductive metallic material is preferably 40 .mu.m or less.
The film thickness is desired to be as small as possible for the
performance of the electromagnetic shielding material because the visible
angle becomes larger as the film thickness is reduced. It is therefore
even more preferable if the film thickness is 18 .mu.m or less. The
plastic film layered by the electroconductive metallic material is
required to be in the form of a continuous roll, and this means that both
the foil of the electroconductive metallic material and the plastic film
are preferably both in the form of continuous rolls. Bonding varnish or a
bonding agent composition is evenly coated over the surface of the foil of
the electroconductive metallic material, and after evaporating the
solvent, the plastic film is laminated over the surface of the
electroconductive metallic material by using a roller laminator to attach
a plastic film to the foil of electroconductive metallic material.
Alternatively, bonding varnish or a bonding agent composition is evenly
coated over the surface of the plastic film, and after evaporating the
solvent, the plastic film is laminated over the surface by using a roller
laminator to attach the plastic film to the foil of electroconductive
metallic material. The thus produced plastic film lined by the foil
electroconductive metallic material is rolled onto a core tube which may
be made of paper, plastic or metal.
The thus produced plastic film layered by the foil of the electroconductive
metallic material is subjected to an etching process so as to form a
geometric pattern and define an aperture ratio of 80% or more. The
geometric pattern as used in this application may consist of a triangle
such as right triangle, equilateral triangle and right-angled triangle, a
rectangle such as square, oblong, parallelepiped and trapezoid; a polygon
such as hexagon, octagon, dodecagon and icosahedron, a circle, an
ellipsoid or a star shape, or a combination of these, and these individual
patterns may repeat by themselves or two or more of these patterns may be
combined. Triangles are most effective in terms of the electromagnetic
shielding effect, but polygons having as many a side as possible are
desirable in view of the transmission factor of visible light because of
an increased aperture ratio.
The geometric pattern may be formed by the chemical etching process which
is widely practiced in the field of printer circuit boards. This process
comprises the step of applying resist ink over the surface of the
electroconductive metallic material layer layered over the plastic film as
a geometric pattern by screen printing. The application of resist ink may
be carried out in a step-wise fashion, by sequentially shifting the area
of resist ink application, and, if necessary, may be accompanied by a
drying process. When the resist pattern is to be formed by using
photosensitive resin film, the photosensitive resin film is layered over a
layer of electroconductive metallic material which is in turn formed over
the surface of plastic film, and photographically exposing the
photosensitive resin film by placing a negative or positive photographic
film, having the geometric pattern printed thereon, over the surface of
the photosensitive resin film. The assembly is then photographically
developed so as to form the geometrically patterned resist layer thereon,
in a continuous manner. Thereafter, the plastic film having the layer of
electroconductive metallic material carrying the geometrically patterned
resist thereon is etched by passing it through a liquid etchant or by
showering a liquid etchant. The assembly is then washed with water, and
dried before it is finally wound into a continuous roll. Obviously, the
process of forming the etching resist layer, and the etching process are
desired to be carried out in a continuous manner in view of increasing the
efficiency. It is effective, in view of increasing the processing
efficiency, to mask the assembly with a chemical etching process, and wind
the assembly as web (or a roll). It is also possible to use a
geometrically patterned mask to selectively, photographically expose and
develop a layer of photosensitive resin which is placed over the surface
of transparent plastic film. Additionally, combining electroless plating
and electric plating is also possible.
The line width of the geometric pattern should be 40 .mu.m or less, the
line spacing should be 200 .mu.m or more, and the line thickness should be
40 .mu.m or less. In view of transmission factor for visible light, it is
even more preferable if the line width is 25 .mu.m or less, the line
spacing is 250 .mu.m or more, and the line thickness is 18 .mu.m or less.
As the line spacing increases, the aperture ratio becomes greater, and the
transmission factor for visible light increases. When the assembly is
applied to the front surface of a display device, the aperture ratio is
required to be 80% or more, but an excessive aperture ratio leads to a
reduction in the electromagnetic shielding performance, and the line
spacing is desired to be 1 mm or less. When the geometric pattern is
relatively complex, the line spacing may be defined by converting the open
area of each repeating pattern unit into a square, and measuring the side
of such a square.
The bonding agent layered over the geometric pattern should have a
refraction index of 1.45 to 1.60. This is because the transmission factor
of visible light diminishes when there is a large difference in refraction
index between the plastic film and the bonding agent layer or between the
bonding agent layer for attaching the electroconductive metallic layer to
the plastic film and the surface bonding agent layer. If the refraction
index is in the range of 1.45 to 1.60, the reduction in the transmission
factor of visible light is insignificant, and a favorable result can be
achieved. In particular, it is desirable if the difference in refractive
index between the bonding agent layer for attaching the electroconductive
metallic layer to the plastic film and the bonding agent layer applied to
the surface of the patterned layer of the electroconductive metallic
material is 0.14 or smaller. This is because if there is a significant
difference between the plastic film and the surface bonding agent, or,
when the plastic film is layered by a layer of electroconductive metallic
material, between the plastic film and the bonding agent between the
metallic layer and the plastic film, the transmission factor of visible
light drops. Such a drop in the transmission factor can be favorably
avoided if the difference in refraction index is 0.14 or less. The
material for the bonding agent meeting such requirements includes
bisphenol type A epoxy resin, bisphenol type F epoxy resin,
tetrahydroxy-phenylmethane epoxy resin novolac epoxy resin, resorcin epoxy
resin, polyalcohol/polyglycohol epoxy resin, polyolefin epoxy resin,
alicyclic epoxy resin and bisphenol halide epoxy resin (which have
refractive indices in the range of 1.55 to 1.60) when the plastic film
consists of polyethylene phthalate (n=1.575, refraction index). In
addition to epoxy resins, dienes such as natural rubber (n=1.52),
polyisoprene (n=1.521), poly-1,2-butadiene (n=1.50), polyisobutane
(n=1.505 to 1.51), polybutane (n=1.5125), poly-2-heptyl-1,3-butadiene
(n=1.50), poly-2-t-butyl-1,3-butadiene (n=1.506) and poly-1,3-butadiene
(n=1.515), polyethers such as polyoxy-ethylene (n=1.4563),
polyvinyl-ethylether (n=1.454), polyvinyl-hexylether (n=1.4591) and
polyvinyl-butylether (n=1.4563), polyesters such as polyvinyl-acetate
(n=1.4665), and polyvinyl-propionete (n=1.4665), polyurethane (n=1.5 to
1.6), ethylcellulose (n=1.479), polyvinyl-chloride (n=1.54 to 1.55),
polyacrylonitrile (n=1.52), polymethyacrylonitrile (n=1.52), polysulfide
(n=1.6), phenoxy resin (n=1.5 to 1.6). These materials are suitable for
achieving a favorable transmission factor for visible light.
When the plastic film is made of acrylic resin, in addition to the above
listed materials, the bonding agent may consist of poly (metha) acrylic
acid esters such as polyethyl-acrylate (n=1.469), polybutyl-acrylate
(n=1.466), poly-2-ethylhexyl-acrylate (n=1.463), poly-t-butyl-acrylate
(n=1.464), poly-3-ethoxypropyl-acrylate (n=1.465),
polyoxycarbonyl-tetramethacrylate (n=1.465), polymethyl-acrylate (n=1.472
to 1.480), polyisopropyl-methacrylate (n=1.473), polydodecil-methacrylate
(n=1.474), polytetradecil-methacrylate (n=1.475),
poly-n-propyl-methacrylate (n=1.484),
poly-3,3,5-trimethyl-cyclohexyl-methacrylate (n=1.484),
polyethyl-methacrylate (n=1.485), poly-2-nitro-2-methylpropyl-methacrylate
(n=1.487), poly-1,1-diethylpropyl-methacrylate (n=1.489), and
polymethyl-methacrylate (n=1.489). Two or more these acrylic polymers may
be copolymerized, or may be mixed together as required.
Copolymers of acrylic resin and other resin material may also be used, and
they include epoxyacrylates, urethanacrylates, polyetheracrylates, and
polyesteracrylates. In terms of bonding property, epoxyacrylates and
polyetheracrylates are particularly desirable. Such epoxyacrylates include
(metha)acrylic acid derivatives such as 1,6-hexandiol-diglycidylether,
neopenthylglycol-diglycidylether, arylalcohol-diglycidylether,
resorcinol-diglycidylether, diglycidylester adipate, diglycidylester
phthalate, polyethyleneglycol-diglycidylesther,
trimethylolpropane-triglycidylether, glycerin-triglycidylether,
pentaerythritol-tetraglycidylether, and sorbitol-tetraglycidylether.
Epoxyacrylates are effective in improving bonding property as they contain
hydroxyl groups in their molecules, and these copolymers can be used
either individually or in combination. The weight-average molecular weight
of the main polymer in the bonding agent should be 1,000 or greater. If
the molecular weight is less than 1,000, the cohesive force of the
composition is so small that a satisfactory attachment to the object may
not be achieved.
The crosslinking/curing agent for the bonding agent may consist of amines
such as triethylenetramine, xylenediamine, N-aminotetramine, and
diaminodiphenylmethane, anhydrides such as anhydrous phtalate acid,
anhydrous maleic acid, anhydrous dodecylsuccinic acid, anhydrous
pyromellitic acid, and anhydrous benzophenontetracarboxylic acid,
diaminodiphenylsulfone, tris(dimethylaminomethyl)phenol, polyamide resins,
dicyandiamide, and ethylmethylimidazol. These materials may be used
individually or in combination. The added amount of the
crosslinking/curing agent should be in the range 0.1 to 50 weight parts,
or more preferably should be in the range of 1 to 30 weight parts for 100
weight parts of the above mentioned polymer. If the added amount is less
than 0.1 weight parts, the crosslinking and curing becomes insufficient.
However, if the added amount exceeds 50 weight parts, the crosslinking may
become excessive, and the bonding property may be impaired as a result.
Diluting agents, plasticizers, oxidation preventing agents, fillers and
adhesion improving agents may be added to the resin composition of the
present invention. The resin composition serving as the bonding agent is
applied over the surface of the plastic film in the form of web or a roll
so as to cover a part of the surface or the entire surface of the plastic
film carrying the geometrically patterned electroconductive metallic layer
and after subjecting the assembly to the processes of drying the solvent,
heating, and partial crosslinking/curing, the assembly is wound into a
roll of the electromagnetic shielding bonding film according to the
present invention. The process of applying the bonding agent having a
refraction index in the range of 1.45 to 1.60 over a part of the surface
or the entire surface of the base material layer can be carried out by
using a coating machine such as a roll coater, a curtain coater or a
gravure coater so as to achieve a uniform thickness. The solvent
components in the bonding agent composition is removed by heating or the
like so as to form a layer of the bonding agent over a part of the surface
or the entire surface of the base material layer including the
geometrically patterned layer of electroconductive metallic material. If
necessary, the bonding agent layer may also be coated over the surface of
the assembly opposite to the surface over which the bonding agent
composition has been applied.
The method for forming the bonding resin composition having an infrared
absorption ratio of 50% or higher for the frequency range of 900 to 1,100
nm may consist of adding organic infrared absorbing agents in the bonding
agent composition. Such organic infrared absorbing agents may include
metal oxides such as iron oxide, cerium oxide, tin oxide and antimony
oxide, indium-tin oxide (which is referred to as ITO hereinafter),
tungsten hexachloride, tin chloride, copper (II) sulfide, chromium-cobalt
complex salt, thiol-nickel complex compound, aminium compounds, diimonium
compounds (marketed by Nihon Kayaku KK), antraquinone compounds (SIR-114),
metallic complex compounds (SIR-128, SIR-130, SIR-132, SIR-159, SIR-152,
and SIR-162), phthalocyanine (SIR-103) (these are marketed by Mitsui
Toatsu Kagaku KK). Alternatively, these compounds may be dispersed in
binder resin which is then over the surface of the bonding agent
composition or the reverse surface of the assembly so as to define an
infrared absorbing layer. The infrared radiation which may emit from the
display device may interfere with the operation of remote controls for
other TVs, VTRs, ratios and personal computers using infrared, and
providing such an Infrared Blocking layer prevents the remote control from
failing to operate properly.
The compounds which are particularly effective in absorbing infrared
radiation include such infrared absorbing agents as copper (II) sulfide,
ITO, aminium compounds, di-imonium compounds, and metallic complex
compounds. In case of infrared absorbing agents other than organic
infrared absorbing agents, it is important to properly select the diameter
of the primary particles. If the particle diameter is substantially larger
than the wavelength of the infrared radiation, the blocking efficiency may
be high, but the transparency drops because the irregular reflection by
the surfaces of the particles cause a hazy appearance. If the particle
diameter is excessively small, the shielding efficiency drops. The
preferable range of the particle diameter is 0.01 to 5 .mu.m, and an even
more preferable range is 0.1 to 3 .mu.m. The infrared absorbing agent is
evenly dispersed in binder resins which may comprise epoxy resins such as
bisphenol type A epoxy resin, bisphenol type F epoxy resin, and novolac
type epoxy resin, diene resins such as polyisoprene, poly-1,2-butadiene,
polyisobutane, and polybutane, polyacrylic acid ester copolymers such as
ethylacrylate, butylacrylate, 2-ethylhexylacrylate, and t-butylacrylate,
polyester resins such as polyvinylacetate, polyvinylpropionate, and
polyolefin resins such as polyethylene, polypropylene, polystyrene, and
EVA. The mixture ratio of the infrared absorbing agent should be
preferably 0.01 to 10 weight parts, and more preferably 0.1 to 5 weight
parts for 100 weight parts of the binder. If the mixture ratio is less
than 0.01 weight parts, a required infrared absorbing ratio cannot be
achieved. If the mixture ratio is greater than 10 weight parts, a required
transparency cannot be achieved. These compounds are applied over the
surface of the bonding agent composition which is geometrically defined on
the surface of the assembly including plastic film and a electroconductive
metallic layer placed over it or the reverse surface of the assembly to a
thickness in the range of 0.01 to 10 .mu.m. The applied layer of the
composition including infrared absorbing compounds may be cured by using
heat or UV.
It is also possible to directly mix the infrared absorbing compounds with
the bonding agent composition. In such a case, the added amount of the
infrared absorbing agent should be in the range of 0.01 to 5 weight parts
for 100 parts of the polymer which forms the bonding agent in view of
shielding performance and transparency.
The anti-reflection process as used in this invention means a process for
increasing the transmission factor of visible light by controlling the
reflection of visible light. The wavelength of minimum reflection is
determined by the thickness of the coating layer, and the refraction index
of the coated material as given by the following equation (Equation 1).
nd=(m+1/2).lambda./2 (1)
where n is the refraction index, d is the thickness of the coating,
.lambda. is the wavelength, and m is an integer 0, 1, 2, 3, . . . )
Because n is determined by the property of the material, the wavelength of
minimum reflection (maximum transmission) can be selected by changing the
thickness of the coating layer. The anti-reflection process may include a
single-layer and multi-layer structures of material having different
refraction indices from that of the transparent plastic film. In the case
of the single-layer structure, the material having a larger refractive
index than the transparent plastic film is selected. When the multi-layer
structure having a favorable anti-reflection effect is selected, it is
desirable to provide a layer of material having a larger refractive index
than the transparent plastic film on the transparent plastic film, and
laminate a layer of material over another in such a manner that the outer
layer may have a larger refractive index than the adjoining inner layer.
The materials for achieving such an anti-reflection property may be
selected from any know materials having such a property, and, for
instance, may include such dielectric materials as CaF.sub.2, MgF.sub.2,
NaAlF.sub.6, Al.sub.2 O.sub.3, SiOx (x=1 or 2), ThF.sub.4, ZrO.sub.2,
Sb.sub.2 O.sub.2, Nd.sub.2 O.sub.2, SnO.sub.2 and TiO.sub.2. The
refractive indices of these materials as well as the thickness of each
layer are selected so that the above mentioned relation may hold. The
anti-reflection layers may be formed by vacuum deposition, ion plating,
sputtering and so on.
The anti-glare process as used in this invention means a process for
preventing the flickering of the display, and the resulting fatigue of the
viewer's eyes, and may be achieved by forming an anti-glare layer which is
made of any known such materials, but preferably from inorganic silica.
However, a hardened film of curable resin material containing inorganic
silica dispersed and secured therein is preferred. Such curable resin
material may include epoxy resins such as bisphenol type A epoxy resin,
bisphenol type F epoxy resin, tetrahydroxy-phenylmethane epoxy resin, and
novolac epoxy resin, diene resins such as polyisoprene,
poly-1,2-butadiene, polyisobutane, and polybutane, polyacrylic acid ester
copolymers such as ethyleneacrylate, butylacrylate, 2-ethyhexylacrylate,
and t-butylacrylate, polyester resins such as polyvinyl-acetate, and
polyvinyl-propionete, polyolefin resins such as polyethylene,
polypropylene, polystyrene, and EVA, and silicone resins.
When forming such an anti-glare layer, first of all, silica particles are
dispersed in crosslinking/curing resin material, and an anti-static agent,
a polymerization initiator, a curing agent, a reaction promoting agent and
other additives are added to the mixture as required. This mixture is
dissolved in a solvent so as to achieve solid content of approximately 20
to 80 weight %. The silica particles are non-crystalline and porous, and
typically consist of silica gel. The average particle diameter should be
30 .mu.m or less, or more preferably in the range of 2 to 15 .mu.m.
Preferably, the content of the silica particles is 0.1 to 10 weight parts
for 100 weight parts of the resin. If the silica content is too small, a
desired anti-glare property may not be obtained. If the silica content is
too large, the transmission factor of visible light and the film strength
may be lost.
This compound may be applied to a surface of the transparent plastic film
by any suitable means such as a gravure coater, a reverse coater, a spray
coater or other known coating machines so that a dry film thickness of 5
to 30 .mu.m may be achieved. The film, after drying with heat, may be
cured and crosslinked by ultraviolet radiation, electron beam radiation or
heating. The anti-glare layer consisting of film containing silica
particles gives a favorable anti-glare property to the assembly when the
transparent plastic film incorporated with this anti-glare layer is bonded
on the surface of the transparent plastic base sheet. Also, because the
anti-glare layer has such a high hardness that a favorable anti-scratch
property is obtained, and the assembly is thereby made highly wear
resistant.
Prior to the formation of such an anti-glare layer, the corresponding
surface or the surface of the transparent plastic film may be subjected to
such preliminary processing as corona discharge processing, plasma
processing, sputter etching and other bonding facilitating measures so
that the adhesive force between the transparent plastic film and the
anti-glare layer may be increased.
According to the present invention, because the surface of the assembly
from which the electronconductive metallic layer has been removed is
deliberately turned into a coarse surface with the aim of improving the
bonding property, and/or the marks of the reverse surface of the
electroconductive metallic layer left on the surface of the assembly, the
transparency is lost to a certain extent. However, by evenly applying a
bonding agent, having a refraction index similar to that of the plastic
film or that of the bonding agent for attaching the electromagnetic
metallic material to the plastic film, onto such an irregular surface,
irregular reflection can be minimized, and the transparency may be
improved. Also, the geometric pattern of the electromagnetic metallic
material layer placed over the plastic film has such a small line width
that the geometric pattern would not be visible to naked eyes. The spacing
between adjacent lines of the geometric pattern is so large that a
virtually transparent appearance would be achieved. The pitch of the
geometric pattern is so small in comparison to the wavelength of the
electromagnetic radiation which is desired to be shielded that a favorable
shielding capability would be achieved.
Thus, according to the method for making electromagnetic shielding bonding
film, comprising the steps of: (a) removing electroconductive metallic
material from plastic film, incorporated with an electroconductive
metallic material layer, by etching so as to define a geometric pattern of
the electroconductive metallic material layer, the geometric pattern
providing an aperture ratio of 80% or more; (b) coating a bonding agent
composition having a refractive index of 1.45 to 1.60 over a part or an
entirety of a base material layer carrying the geometric pattern; and (c)
coating a resin composition having an absorption ratio of 50% or more for
infrared light of 900 to 1,100 nm in wavelength over the surface coated
with the bonding agent composition or the opposite surface; the film being
continually paid from a roll and wound back to a roll in each of the
steps, because the manufacturing process can be carried out in a
continuous manner in each step involving very little waste of material and
energy, it is possible to manufacture a highly workable and high-quality
electromagnetic shielding bonding film in a highly waste-free and
efficient manner.
Also, according to the method for making electromagnetic shielding bonding
film, comprising the steps of: (a) removing electroconductive metallic
material from plastic film, incorporated with an electroconductive
metallic material layer, by etching so as to define a geometric pattern of
the electroconductive metallic material layer, the geometric pattern
providing an aperture ratio of 80% or more; and (b) coating a resin
composition having a refractive index of 1.45 to 1.60 and an absorption
ratio of 50% or more for infrared light of 900 to 1,100 nm in wavelength
over a part or an entirety of a base material layer carrying the geometric
pattern; the film being continually paid from a roll and wound back to a
roll in each of the steps, because the manufacturing process can be
carried out in a continuous manner in each step involving very little
waste of material and energy in a similar fashion, it is possible to
manufacture a highly workable and high-quality electromagnetic shielding
bonding film in a highly waste-free and efficient manner.
According to the present invention, the step of attaching the
electroconductive metallic material to the plastic film, the step of
geometrically patterning the electroconductive metallic material, and the
step of forming the bonding agent layer by applying the bonding agent to
the assembly can be carried either entirely continually, or in a partly
continuous manner. The thus fabricated electromagnetic shielding bonding
film may be attached to one side of a plastic base board such as acrylic
plate or polyester plate, or may be laminated between a pair of such
plastic base boards, and after being appropriately trimmed, the assembly
may be used in a display device.
The thus obtained bonding film having an electromagnetic shielding and
infrared blocking property can be directly attached to a display device
such as CRT, PDP, LCD, and EL, by using the bonding agent included in the
bonding film, or may be attached to a plate or a sheet such as an acrylic
plate or a glass sheet for mounting the thus prepared assembly on a
display device. The bonding film may also be used on the cases of
measuring devices, measuring instruments and manufacturing devices, and
inspection windows provided in such cases. The present invention may also
be applied to windows of building and vehicles which may be exposed to
electromagnetic interferences from radio towers and high tension electric
cables. It is preferable to provide a grounding line in the geometrically
patterned electroconductive material.
The electromagnetic shielding bonding film may be continuously laminated
over the plastic base board by using a roller laminator and continually
feeding the plastic base board.
The plastic base board preferably is colorless and transparent, but may
also be tinted as long as it has a required transparency. Preferably, the
thickness is in the range of 0.5 to 10 mm, and the transmission factor for
all visible light range is 50% or more, or, more preferably, 80% or more.
Typically materials for the plastic base board includes polycarbonate,
polymethyl(metha)acrylate, polyethyleneterephthalate, polyether sulfone,
polyetherketone, and acyronitrile-styrene copolymer.
An infrared absorption ratio of 50% or more in the wavelength range of 800
to 1,100 nm can be achieved in the bonding film by mixing organic infrared
absorbing agents in the above mentioned bonding agent, or by applying a
composition containing such organic infrared absorbing agents in a binder
over the bonding agent layer surface or the reverse surface of the bonding
film. Such organic infrared absorbing agents may include metal oxides such
as iron oxide, cerium oxide, tin oxide and antimony oxide, indium-tin
oxide (which is referred to as ITO hereinafter), tungsten hexachloride,
tin chloride, copper (II) sulfide, chromium-cobalt complex salt,
thiol-nickel complex compound, aminium compounds, and diimonium compounds
(marketed by Nihon Kayaku KK). The compounds which are particularly
effective in absorbing infrared radiation include such infrared absorbing
agents as copper (II) sulfide, ITO, aminium compounds, di-imonium
compounds, and metallic complex compounds. It is important to properly
select the diameter of the primary particles. If the particle diameter is
substantially larger than the wavelength of the infrared radiation, the
blocking efficiency may be high, but the transparency drops because the
irregular reflection by the surfaces of the particles cause a hazy
appearance. If the particle diameter is excessively small, the shielding
efficiency drops. The preferable range of the particle diameter is 0.01 to
5 .mu.m, and an even more preferable range is 0.1 to 3 .mu.m. The infrared
absorbing agent is evenly dispersed in binder resins which may comprise
epoxy resins such as bisphenol type A epoxy resin, bisphenol type F epoxy
resin, and novolac type epoxy resin, diene resins such as polyisoprene,
poly-1,2-butadiene, polyisobutane, and polybutane, polyacrylic acid ester
copolymers such as ethylacrylate, butylacrylate, 2-ethylhexylacrylate, and
t-butylacrylate, polyester resins such as polyvinylacetate,
polyvinylpropionate, and polyolefin resins such as polyethylene,
polypropylene, polystyrene, and EVA. The mixture ratio of the infrared
absorbing agent should be preferably 0.1 to 10 weight parts, and more
preferably 0.1 to 5 weight parts for 100 weight parts of the binder. If
the mixture ratio is less than 0.01 weight parts, a required infrared
absorbing ratio cannot be achieved. If the mixture ratio is greater than
10 weight parts, a required transparency cannot be achieved. These
compounds are applied over the surface of the bonding agent layer of the
bonding film or the reverse surface of the bonding film to a thickness in
the range of 0.01 to 10 .mu.m. The applied layer of the composition
including infrared absorbing compounds may be cured by using heat or UV.
It is also possible to directly mix the infrared absorbing compounds with
the bonding agent composition. In such a case, the added amount of the
infrared absorbing agent should be in the range of 0.01 to 5 weight parts
for 100 parts of the polymer which forms the bonding agent in view of
shielding performance and transparency.
The part of the surface of the transparent plastic base member from which
the electroconductive material has been removed presents an irregular
surface because the surface was deliberately formed into an irregular
surface in order to increase the adhesion force or because the marks of
the reverse surface of the electroconductive material were imprinted on
the surface of the transparent plastic base member. Therefore, the
irregular reflection on the surface may damage the transparency of the
base member, but by evenly applying a resin material layer, having a
refraction index close to that of the base member, over such an irregular
surface, the irregular reflection is minimized so that the transparency of
the base member may be restored. The electroconductive material
geometrically patterned on the surface of the transparent plastic base
member has such a fine line width that it is practically invisible to
naked eyes. The large line spacing also contributes to the invisibility of
the electroconductive material. Also, it is believed that, because the
pitch of the geometric pattern is sufficiently smaller than the wavelength
of the electromagnetic radiation that is desired to be shielded, a
superior shielding performance can be achieved.
EXAMPLE
Electromagnetic Shielding Bonding Film #A1
The plastic film consisted of transparent PET film having the thickness of
50 .mu.m and the roll length of 300 m (marketed by Toyo Boseki KK under
the tradename of A-4100, refraction index n=1,575). An electrolytic copper
foil having the thickness of 18 .mu.m was laminated thereover, by heating,
under the condition of 180.degree. C. and 30 kgf/cm.sup.2, in continuous
manner from the beginning to the end of the roll over the surface of the
plastic film via an epoxy bonding film (marketed by Nikkan Kogyo KK under
the tradename of Nikaflex, n=1.58, thickness 20 .mu.m), serving as a
bonding layer, with the coarse surface of the copper foil facing the epoxy
bonding film.
The obtained roll of PET film laminated with copper foil is subjected to a
photo-lithographic process (including the steps of resist film coating,
photographic exposure, photographic development, chemical etching, and
resist film removal), and a copper grid pattern having the line width of
25 .mu.m and the line spacing of 500 .mu.m was formed on the surface of
the PET film by spraying ferrous chloride liquid etchant. After the resist
was removed, the assembly was subjected to the steps of water washing, and
drying, and a roll of Composition #A1 was obtained in a continuous manner
from the beginning to the end of the roll. The obtained roll was free from
creases or other visible defects. The transmission factor of Composition
#A1 for visible light was 20% or less. A bonding agent composition
containing an infrared absorbing agent which is described hereinafter was
continuously applied over the surface of Composition #A1 to the dry
thickness of approximately 40 .mu.m, and after a drying process,
Electromagnetic Shielding Bonding Film #A1 having an electromagnetic
shielding property and a transparency was obtained as a roll which is
continuous from the beginning to the end. Thereafter, Electromagnetic
Shielding Bonding Film #A1 was applied over the surface of commercially
available acrylic plate (marketed by KK Kurare under the tradename of
Komoglass, thickness 3 mm), as the acrylic plate is fed out, by using a
roll laminator with the surface of the bonding agent facing the acrylic
plate under the temperature and pressure condition of 110.degree. C. and
20 kgf/cm.sup.2. The material for display devices is thus made in a
continuous manner, and is cut into the required size. The cut material was
then properly trimmed, and used for the fabrication of a display device.
EXAMPLE
Electromagnetic Shielding Bonding Film #A2
Aluminum foil having the thickness of 25 .mu.m was bonded over the surface
of PET film having the thickness of 25 .mu.m and the roll length of 400 m
via acrylic bonding film (marketed by DuPont under the tradename of
Pyralux LF-0200, n=1.47, thickness 20 .mu.m). This assembly consisting of
PET film laminated with aluminum foil is subjected to a photo-lithographic
process similar to that for Electromagnetic Shielding Bonding Film #A1,
and an aluminum grid pattern having the line width of 25 .mu.m and the
line spacing of 250 .mu.m was formed on the surface of the PET film by
spraying a hydrochloric acid liquid etchant. After the resist film was
removed, the assembly was subjected to the steps of water washing, and
drying, and a roll of Composition #A2 was obtained in a continuous manner
from the beginning to the end of the roll. The transmission factor of
Composition #A2 for visible light was 20% or less. A bonding agent
composition containing an infrared absorbing agent which is described
hereinafter, was continuously applied over the surface of Composition #A2
to the dry thickness of approximately 30 .mu.m, and after a drying
process, Electromagnetic Shielding Bonding Film #A2 having an
electromagnetic shielding property and a transparency was obtained as a
roll which is continuous from the beginning to the end. The obtained roll
was free from creases or other visible defects. Thereafter,
Electromagnetic Shielding Bonding Film #A2 was applied over the surface of
commercially available acrylic plate (marketed by KK Kurare under the
tradename of Komoglass, thickness 3 mm) by using a thermal press with the
surface of the bonding agent facing the acrylic plate under the
temperature and pressure condition of 110.degree. C., 30 kgf/cm.sup.2, and
30 minutes. The material was then properly trimmed, and used for the
fabrication of a display device.
EXAMPLE
Electromagnetic Shielding Bonding Film #A3
Electroless nickel plating to the thickness of 2 .mu.m was applied over the
surface of PET film having the thickness of 50 .mu.m and the roll length
of 300 m via an additive bonding agent layer (n=1.57) having the thickness
of 20 .mu.m. This assembly is subjected to a photo-lithographic process
similar to that for Electromagnetic Shielding Bonding Film #A1, and a
nickel grid pattern having the line width of 12 .mu.m, the line spacing of
500 .mu.m, and the thickness of 2 .mu.m was formed on the surface of the
PET film by spraying ferrous chloride liquid etchant. After the resist
film was removed, the assembly was subjected to the steps of water
washing, and drying, and a roll of Composition #A3 was obtained in a
continuous manner from the beginning to the end of the roll. The
transmission factor of Composition #A3 for visible light was 20% or less.
A bonding agent which is described hereinafter was continuously applied
over the surface of Composition #A3 carrying the geometric pattern to the
dry thickness of approximately 70 .mu.m, and after a drying process, an
Infrared Blocking layer (1) which is described hereinafter was applied
over the reverse surface of the PET film to the thickness of 3 .mu.m in a
continuous manner. After the final drying process, Electromagnetic
Shielding Bonding Film #A3 having an electromagnetic shielding property
and a transparency was obtained as a roll which is continuous from the
beginning to the end. The obtained roll was free from creases or other
visible defects.
Thereafter, Electromagnetic Shielding Bonding Film #A3 was applied over the
surface of commercially available acrylic plate (marketed by KK Kurare
under the tradename of Komoglass, thickness 3 mm) by using a roller
laminator with the surface of the bonding agent facing the acrylic plate
under the temperature and pressure condition of 110.degree. C. and 20
kgf/cm.sup.2. The material for display devices is thus made in a
continuous manner, and is cut into the required size. The cut material was
then properly trimmed, and used for the fabrication of a display device.
<Bonding Agent Composition #A1>
TBA-HME (Hitachi Kasei Kogyo KK; 100 weight parts
high polymer epoxy resin, Mw = 300,000)
YD-8125 Toto Kasei Kogyo KK; 25 weight parts
bisphenol type A epoxy resin)
IPDI (Hitachi Kasei Kogyo KK; 12.5 weight parts
mask isophorone-di-isioyanate)
2-ethyl-4-methylimidazole 0.3 weight parts
SIR-159 (Mitsui Toatsu Kagaku KK, 1.4 weight parts
infrared absorbing agent)
MEK (methyl-ethyl-ketone) 330 weight parts
cyclohexanone 15 weight parts
The refraction index of Bonding Agent Composition #A1 after drying the
solvent was 1.57.
<Bonding Agent Composition #A2>
YP-30 (Toto Kasei KK, 100 weight parts
phenoxy resin, Mw = 60,000)
YD-8125 (Toto Kasei Kogyo KI; 10 weight parts
bisphenol type A epoxy resin)
IPDI (Hitachi Kasei Kogyo KK; 5 weight parts
mask-isophorone-di-isocyanate)
2-ethyl-4-methylimidazole 0.3 weight parts
IRG-022 (Nihon Kayaku KK, 1.2 weight parts
di-imonium compound, infrared absorbing agent)
MEK 285 weight parts
cyclohexanone 5 weight parts
The refraction index of Bonding Agent Composition #A2 after drying the
solvent was 1.55.
<Bonding Agent Composition #A3>
HTR-600LB (Teikoku Kagaku Sangyo KK, 100 weight parts
polyacrylic acid ester, Mw = 700,000)
Colonate L (Nihon Polyurethane Kogyo KK, 4.5 weight parts
3-functional isocyanate)
dibutyl-tin laurate 0.4 weight parts
toluen 450 weight parts
ethylacetate 10 weight parts
The refraction index of Bonding Agent Composition #A3 was 1.47.
<Infrared Blocking Layer Composition #A1>
HTR-280 (Teikoku Kagaku Sangyo KK, 100 weight parts
polyacrylic acid ester copolymer, Mw = 700,000)
(UFP-HX (Sumitomo Kinzoku Kozan KK, 0.5 weight parts
ITO, average particle diameter 0.1 .mu.m)
Colonate L (Nihon Polyurethane Kogyo KK, 5 weight parts
3-functional isocyanate)
dibutyl-tin laurate 0.4 weight parts
toluen 450 weight parts
ethylacetate 10 weight parts
The composition was applied by using a roll coater, and was cured at
90.degree. C. for 20 minutes, and the cured layer had a refraction index
of 1.49.
Infrared Blocking Layer Composition #A2
Infrared Blocking Layer Composition #A2 was used in a similar manner except
for that one weight part of copper (II) sulfide (Wako Junyaku KK; crushed
to the average particle diameter of 0.5 .mu.m by using a Henschel mixer)
instead of UFP-HX of Infrared Blocking Layer Composition #A2. The obtained
composition has a refraction index of 1.50.
Example #A1
Example #A1 consists of a display device which was formed according to the
method of making Electromagnetic Shielding Bonding Film #A1 by using
Bonding Agent Composition #A1.
Example #A2
Example #A2 consists of a display device which was formed according to the
method of making Electromagnetic Shielding Bonding Film #A2 by using
Bonding Agent Composition #A2.
Example #A3
Example #A3 consists of a display device which was formed according to the
method of making Electromagnetic Shielding Bonding Film #A1 by using
Bonding agent Composition #A3 and Infrared Blocking Layer Composition #A1.
Example #A4
A display device which was prepared identically as the display device of
Example #A1 except for that the line width was 35 .mu.m instead of 25
.mu.m.
Example #A5
A display device which was prepared identically as the display device of
Example #A2 except for that the line width was 12 .mu.m instead of 25
.mu.m.
Example #A6
A display device which was prepared identically as the display device of
Example #A3 except for that the line spacing was 800 .mu.m instead of 500
.mu.m, and Infrared Blocking Layer Composition #A2 was used instead of
Infrared Blocking Layer Composition #A1.
Example #A7
A display device which was prepared identically as the display device of
Example #A1 except for that the line spacing was 250 .mu.m instead of 500
.mu.m.
Example #A8
A display device which was prepared identically as the display device of
Example #A2 except for that the line thickness was 35 .mu.m instead of 25
.mu.m.
Example #A9
A display device which was prepared identically as the display device of
Example #A1 except for that the electroconductive metallic material
consisted of darkened copper.
Example #A10
A display device which was prepared identically as the display device of
Example #A1 except for that the geometric pattern consisted of a
repetition of a right triangle instead of the grid pattern of Example #A1.
Example #A11
A display device which was prepared identically as the display device of
Example #A1 except for that the geometric pattern consisted of a
repetition of a right hexagon instead of the grid pattern of Example #A1.
Example #A12
A display device which was prepared identically as the display device of
Example #A1 except for that the geometric pattern consisted of a
repetition of a right octagon and a square instead of the grid pattern of
Example #A1.
Comparative Example #A1
Bonding Agent Composition #A1 was directly applied over the surface of PET
film over which ITO film was deposited to the thickness of 2,000 .ANG. by
vapor deposition, instead of the patterned copper foil. The assembly was
used for preparing a display device in the same way as Example #A1.
Comparative Example #A2
Similarly as Comparative Example #A1, Bonding Agent Composition #A2 was
directly applied over the surface of PET film over which ITO film was
deposited to the thickness of 2,000 .ANG. by vapor deposition, instead of
the patterned copper foil. The assembly was used for preparing a display
device in the same way as Comparative Example #A1.
Comparative Example #A3
Comparative Example #A3 consisted of a display device which was prepared
identically as the display device of Example #A1 except for that the line
width was 50 .mu.m instead of 25 .mu.m.
Comparative Example #A4
Comparative Example #A4 consisted of a display device which was prepared
identically as the display device of Example #A2 except for that the line
spacing was 150 .mu.m instead of 250 .mu.m.
Comparative Example #A5
Comparative Example #A5 consisted of a display device which was prepared
identically as the display device of Example #A2 except for that the line
thickness was 70 .mu.m instead of 25 .mu.m.
The infrared blocking ratio, electromagnetic shielding performance, visible
light transmission factor, invisibility, bonding property before and after
curing, fading property, and roll appearance of the electromagnetic
shielding bonding films and the display devices were actually measured,
and the measured results are summarized in Tables 1 and 2.
The infrared blocking ratio was measured as an average value of the
infrared absorption ratio for the wavelength range of 900 to 1,000 nm by
using a spectrophotometer (marketed by KK Hitachi Seisakusho under the
tradename of U-3410).
The electromagnetic shielding performance was measured by placing the
specimen between two flanges of a coaxial waveguide converter (market by
Nihon Koshuha KK under the tradename of TWC-S-024), and using a
spectro-analyzer (marketed by YHP under the tradename of 8510B Vector
Network Analyzer) at the frequency of 1 GHz.
The visible light transmission factor was measured as an average value of
the transmission factor over the wavelength range of 400 to 800 nm by
using a double beam spectro-photoanalyzer (marketed by KK Hitachi under
the tradename of Type 200-10).
The invisibility was measured by placing the display device at the distance
of 0.5 m, and evaluating if the geometric pattern of the electroconductive
metallic material is visible or not. The specimens were graded into "very
good", and "good" depending on the degree of invisibility, and "NG" when
the pattern was visible.
The bonding property was measured by using a tensile strength testing
machine (marketed by Toyo Baldwin KK under the tradename of Tensilon
UTM-4-100) with the width of 10 mm, 90 degree direction and peeling speed
of 50 mm/minute.
The refraction index was measured by using a refraction meter (marketed by
KK Atago Kogaku Kikai Seisakusho under the tradename of Abbe refraction
meter) at the temperature of 25.degree. C.
TABLE 1
examples
items #A1 #A2 #A3 #A4 #A5 #A6 #A7 #A8 #A9 #A10 #A11
#A12
method of forming foil foil plating foil foil plating
foil foil foil foil foil foil
conductive layer bonding bonding bonding bonding
conductive material Cu Al Ni Cu Al Ni Cu
Al darkened Cu Cu Cu
Cu
plastic film PET PET PET PET PET PET PET
PET PET PET PET PET
shape square square square square square square
square square square right right octagon +
triangle hexagon square
patterning method *1 CE CE M CE CE M CE
CE CE CE CE CE
line width (.mu.m) 25 25 12 35 12 12 25
25 25 25 25 25
line spacing (.mu.m) 500 250 500 500 250 800 250
250 500 500 500 500
line thickness (.mu.m) 18 25 2 18 25 2 18
35 18 18 18 18
bonding agent #A1 #A2 #A3 #A1 #A2 #A3 #A1 #A2 #A1 #A1 #A1 #A1
composition *2
EMI shielding 50 40 48 56 38 30 55
56 48 54 50 48
performance
visible light transmission 74 69 70 68 75 77
70 69 70 69 75 77
factor (%)
invisibility good good good good good good
good good very good good good
good
infrared blocking ratio 80 78 80 65 65 65 80
80 80 80 80 80
(%)
initial bonding force 1.2 1.7 0.9 1.2 1.7 1.7 1.2
1.7 1.2 1.2 1.1 1.1
(kgf/cm.sup.2)
bonding force after 80.degree. C.- 1.2 1.5 0.8 1.2 1.6
1.5 1.2 1.5 1.2 1.2 1.1 1.1
1,000 hrs of aging
fading after 80.degree. C.- none none none none none none
none none none none none none
1,000 hrs of aging
web appearance good good good good good good
good good good good good good
*1 CE: chemical deposition, M: plating
*2 #A1: Bonding Agent Composition #A1, #A2: Bonding Agent Composition #A2,
and #A3: Bonding Agent Composition #A3.
TABLE 2
comparative examples
items #A1 #A2 #A3 #A4 #A5
method of forming vapor deposition vapor deposition foil foil
foil
conductive layer
conductive material ITO Al Cu Al Al
plastic film PET PET PET PET PET
shape entire surface entire surface square square
square
patterning method*1 -- -- CE CE CE
line width (.mu.m) -- -- 50 25 25
time spacing (.mu.m) -- -- 500 150 250
time thickness (.mu.m) 0.2 0.2 18 25 70
bonding agent composition*2 #A1 #A2 #A1 #A2 #A2
EMI shielding performation 18 35 39 37 45
visible light transmission 85 20> 55 40 60
factor (%)
invisibility good NG NG NG NG
infrared blocking ratio (%) 10> 10> 10> 10> 10>
initial bonding force 1.2 1.7 1.2 1.7 0.9
(kgf/cm.sup.2)
bonding force after 80.degree. C.- 1.2 1.5 1.2
1.5 0.8
1,000 hrs of aging
fading after 80.degree. C.- none none none none
none
1,000 hrs of aging
web appearance good good good good good
*1-CE: chemical deposition, M: plating
*2-#A1: Bonding Agent Composition #A1,#A2: Bonding Agent Composition #A2,
and #A3: Bonding Agent Composition #A3
Comparative Examples #A1 and #A2 involve vapor deposition of ITO and A1,
respectively, but ITO lacks the desired electromagnetic shielding
property, and A1 lacks the desired visible light transmission factor.
Comparative Example #A3 has a low visible light transmission factor with
the broad line width of 50 .mu.m, and a poor invisibility whereas the
present invention features an aperture ratio of 80% or better, and a line
width of 40 .mu.m or less. Comparative Example #A4 has a low visible light
transmission factor with the narrow line spacing of 150 .mu.m similarly as
Comparative Example #A3, and a poor invisibility whereas the present
invention features an aperture ratio of 80% or better, and a line spacing
of 200 .mu.m or wider. Comparative Example #A5 has a poor invisibility
with the line thickness of 70 .mu.m whereas the present invention features
an aperture ratio of 80% or better, and a line thickness of 40 .mu.m or
less. On the other hand, Examples #A1 to #A12 according to the present
invention all demonstrate favorable electromagnetic shielding properties
of 30 dB or better. The present invention also provides a visible light
transmission factor of 68% or better, and a favorable invisibility. The
initial bonding force and the bonding force after 1,000 hours of an aging
test at 80.degree. C. are sufficiently high, and the web appearance is
also favorable.
As can be appreciated from the description of the above examples, the
electromagnetic shielding bonding film of the present application can
provide a favorable infrared blocking property, and its capability to
closely attach to the object allows a high electromagnetic shielding
performance without involving substantially any electromagnetic leakage.
The present invention further provides favorable optical properties such
as a high visible light transmission factor, and a favorable invisibility.
The bonding film according to the present invention can maintain a
superior bonding force even at high temperatures over an extended time
period, and can be made available as web (or as a roll) without involving
any visible defects such as creases. By using polyethylene-terephthalate
film for the plastic film, a highly transparent, heat-resistance,
economical and easy handling electromagnetic shielding bonding film can be
obtained. By using a layer of copper, aluminum or nickel having a
thickness of 3 to 40 .mu.m for the electroconductive metallic material
layer, and making the surface of the layer facing the transparent plastic
film into a coarse surface, a highly workable and economical
electromagnetic shielding bonding film can be obtained. By using copper
having at least its outer surface darkened, a fade-resistant and
high-contrast electromagnetic shielding bonding film can be obtained. By
using paramagnetic metal for the electroconductive metallic material, an
electromagnetic shielding bonding film having a high electromagnetic
shielding property can be obtained. When this electromagnetic shielding
bonding film is applied to a display device, a display device having a
favorable electromagnetic shielding property, a high visible light
transmission factor, and a favorable invisibility, and capable of
displaying clear images can be obtained.
EXAMPLE
Bonding Film #B1
The plastic film consisted of transparent PET film having the thickness of
50 .mu.m (refraction index n=1,575). An electrolytic copper foil having
the thickness of 18 .mu.m was laminated thereover, by heating, under the
condition of 180.degree. C. and 30 kgf/cm.sup.2, via an epoxy bonding
sheet (marketed by Nikkan Kogyo KK under the tradename of Nikaflex,
n=1.58), serving as a bonding layer, with the coarse surface of the copper
foil facing the epoxy bonding sheet.
The obtained PET film laminated with copper foil is subjected to a
photo-lithographic process (including the steps of resist film coating,
photographic exposure, photographic development, chemical etching, and
resist film removal), and a copper grid pattern having the line width of
25 .mu.m and the line spacing of 500 .mu.m was formed on the surface of
the PET film to obtain Composition #B1. The visible light transmission
factor of Composition #B1 was 20% or less. A bonding agent which is
described hereinafter was applied over the surface of Composition #B1
carrying the geometric pattern to the dry thickness of approximately 40
.mu.m, and after a drying process, Bonding Film #B1 having an
electromagnetic shielding property and an optical transparency was
obtained. An infrared blocking layer which is described hereinafter was
applied to the surface of Bonding Film #B1 opposite to the surface
carrying the bonding agent layer, to the dry thickness of approximately 5
.mu.m. Thereafter, Bonding Film #B1 was applied over the surface of
commercially available acrylic plate (marketed by KK kurare under the
tradename of Komoglass, thickness 3 mm) by using a roll laminator under
the temperature and pressure condition of 110.degree. C. and 20
kgf/cm.sup.2.
EXAMPLE
Bonding Film #B2
Aluminum foil having the thickness of 25 .mu.m was bonded over the surface
of PET film having the thickness of 25 .mu.m serving as the transparent
base material via acrylic bonding film (marketed by DuPont under the
tradename of Pyralux LF-0200, n=1.47). This assembly consisting of PET
film laminated with aluminum foil is subjected to a photo-lithographic
process similar to that for Bonding Film #1, and an aluminum grid pattern
having the line width of 25 .mu.m and the line spacing of 250 .mu.m was
formed on the surface of the PET film to obtain. The visible light
transmission factor of this assembly was 20% or less. A bonding agent
which is described hereinafter was applied over the surface of this
assembly carrying the geometric pattern to the dry thickness of
approximately 30.mu.m, and after a drying process, bonding Film #B2 having
an electromagnetic shielding property and an optical transparency was
obtained. An infrared blocking layer which is described hereinafter was
applied to the surface of Bonding Film #B2 opposite to the surface
carrying the bonding agent layer, to the dry thickness of approximately 1
.mu.m. Thereafter, Bonding Film #B2 was applied over the surface of
commercially available acrylic plate by using a thermal press under the
temperature and pressure condition of 110.degree. C., 30 kgf/cm.sup.2 and
30 minutes.
EXAMPLE
Bonding Film #B3
Electroless nickel plating was applied over the surface of PET film having
the thickness of 50 .mu.m by using a mask so as to form a nickel grid
pattern having the line width of 12 .mu.m, the line spacing of 500 .mu.m,
and the thickness of 2 .mu.m. The visible light transmission factor of
this assembly was 20% or less. A bonding agent which is described
hereinafter was applied over the surface of this assembly carrying the
geometric pattern to the dry thickness of approximately 70 .mu.m. An
infrared blocking layer which is described hereinafter was applied to the
surface of Bonding Film #B3 opposite to the surface carrying the bonding
agent layer, to the dry thickness of approximately 3 .mu.m. Thereafter,
Bonding Film #B3 was applied over the surface of commercially available
acrylic plate by using a roll laminator under the temperature and pressure
condition of 110.degree. C., 20 kgf/cm.sup.2.
<Bonding Agent Composition #B1>
TBA-HME (Hitachi Kasei Kogyo KK; 100 weight parts
high polymer epoxy resin, Mw = 300,000)
YD-8125 (Toto Kasei Kogyo KK; 25 weight parts
bisphenol type A epoxy (resin)
IPDI (Hitachi Kasei Kogyo KK; 12.5 weight parts
mask isophorone-di-isocyanate)
2-ethyl-4-methylimidazole 0.3 weight parts
MEK (methyl-ethyl-ketone) 330 weight parts
cyclohexanone 15 weight parts
The refraction index of this composition after drying the solvents was
1.57.
<Bonding Agent Composition #B2>
YP-30 (Toto Kasei KK, 100 weight parts
phenoxy resin, Mw = 60,000)
YD-8125 (Toto Kasei Kogyo KK; 10 weight parts
bisphenol type A epoxy resin)
IPDI (Hitachi Kasei Kogyo KK; 5 weight parts
mask-isocyanate)
2-ethyl-4-methylimidazole 0.3 weight parts
MEK 285 weight parts
cyclohexanone 5 weight parts
The refraction index of this composition after drying the solvents was
1.55.
<Bonding Agent Composition #B3>
HTR-600LB (Teikoku Kagaku Sangyo KK, 100 weight parts
polyacrylic acid ester, Mw = 700,000)
Colonate L (Nihon Polyurethane Kogyo KK, 4.5 weight parts
3-functional isocyanate)
dibutyl-tin laurate 0.4 weight parts
toluen 450 weight parts
ethylacetate 10 weight parts
The refraction index of this composition after drying the solvents was
1.47.
<Infrared Blocking Layer Composition #B1>
YD-8125 (Toto Kasei Kogyo KK; 100 weight parts
bisphenol type A epoxy resin)
copper (II) sulfide (Wako Junyaku KK, crushed 4 weight parts
to an average particle diameter of 0.5 .mu.m
by using a Henschel mixer)
2-ethyl-3-methylimidazol 0.5 weight parts
dicyandiamide 5 weight parts
MEK 200 weight parts
etyleneglycol-monomethyether 20 weight parts
The compound was applied with an applicator at room temperature, and was
cured by heating at 90.degree. C. for 30 minutes.
<Infrared Blocking Layer Composition #B2>
HTR-280 (Teikoku Kagaku Sangyo KK, 100 weight parts
polyacrylic acid ester copolymer, Mw = 700,000)
UFP-HX (Sumitomo Kinzoku Kozan KK, 0.5 weight parts
ITO, average particle diameter 0.l .mu.m)
Colonate L 5 weight parts
dibutyl-tin laurate 0.4 weight parts
toluen 450 weight parts
ethylacetate 10 weiglit parts
The compound was applied with an applicator at room temperature, and was
cured by heating at 90.degree. C. for 20 minutes.
<Infrared Blocking Layer Composition #B3>
copper (II) sulfide (Wako Junyaku KK; crushed 1 weight part
to the average particle diameter of 0.5 .mu.m
by using a Henschel mixer)
EXAMPLE #B1
Example #B1 consists of shield plate which was prepared according to the
procedure for preparing Bonding Film Composition #B1 by using Bonding
Agent Composition #B1 and Infrared Blocking Layer Composition #B1.
EXAMPLE #B2
Example #B2 consists of shield plate which was prepared according to the
procedure for preparing Bonding Film Composition #B2 by using Bonding
Agent Composition #B2 and Infrared Blocking Layer Composition #B1.
EXAMPLE #B3
Example #B3 consists of shield plate which was prepared according to the
procedure for preparing Bonding Film Composition #B3 by using Bonding
Agent Composition #B3 and Infrared Blocking Layer Composition #B1.
EXAMPLE #B4
Example #B4 consists of shielding plate which was identically prepared as
Example #B1 except for that the line width was 35 .mu.m instead of 25
.mu.m and Infrared Blocking Layer Composition #B2 was used instead of #B1.
EXAMPLE #B5
Example #B5 consists of shielding plate which was identically prepared as
Example #B2 except for that the line width was 12 .mu.m instead of 25
.mu.m and Infrared Blocking Layer Composition #B2 was used instead of #B1.
EXAMPLE #B6
Example #B6 consists of shielding plate which was identically prepared as
Example #B3 except for that the line spacing was 800 .mu.m instead of 500
.mu.m and Infrared Blocking Layer Composition #B2 was used instead of #B1.
EXAMPLE #B7
Example #B7 consists of shielding plate which was identically prepared as
Example #B1 except for that the line spacing was 250 .mu.m instead of 500
.mu.m.
EXAMPLE #B8
Example #B8 consists of shielding plate which was identically prepared as
Example #B2 except for that the line spacing was 35 .mu.m instead of 25
.mu.m.
EXAMPLE #B9
Example #B6 consists of shielding plate which was identically prepared as
Example #B1 except for that the electroconductive material consisted of
darkened copper and Infrared Blocking Layer Composition #B2 was used
instead of #B1.
EXAMPLE #B10
Example #B10 consists of shielding plate which was identically prepared as
Example #B1 except for that the geometric pattern consisted of a
repetition of a right triangle instead of the grid pattern of Example #B1
and Infrared Blocking Layer Composition #B2 was used instead of #B1.
EXAMPLE #B11
Example #B11 consists of shielding plate which was identically prepared as
Example #B1 except for that the geometric pattern consisted of a
repetition of a right hexagon instead of the grid pattern of Example #B1
and one weight part of Infrared Blocking Layer Composition #B3 was
dispersed in 100 weight parts of the bonding agent.
EXAMPLE #B12
Example #B12 consists of shielding plate which was identically prepared as
Example #B1 except for that the geometric pattern consisted of a
repetition of a right octagon and a square instead of the grid pattern of
Example #B1 and one weight part of Infrared Blocking Layer Composition #B3
was dispersed in 100 weight parts of the bonding agent.
COMPARATIVE EXAMPLE #B1
PET film over which ITO film was vapor deposited to the thickness of 2,000
.ANG. by vapor deposition, instead of the patterned copper foil, was used.
Bonding Agent Composition #B1 was directly applied over the assembly
without geometrically patterning the ITO film. Thereafter, shielding plate
was prepared therefrom in the same way as Example #B1 without forming an
infrared blocking layer to obtain Comparative Example #B1.
COMPARATIVE EXAMPLE #B2
Transparent PET film serving as the transparent plastic base member, over
which aluminum film was vapor deposited, was used. Bonding Agent
Composition #B2 was directly applied over the surface of the assembly
without geometrically patterning the aluminum film. Thereafter, shielding
plate was prepared therefrom in the same way as Example #B1 to obtain
Comparative Example #B2.
COMPARATIVE EXAMPLE #B3
Comparative Example #B3 consisted of shielding plate which was prepared
identically as the shielding plate of Example #B1 except for that the line
width was 50 .mu.m instead of 25 .mu.m, and no infrared blocking layer was
formed.
COMPARATIVE EXAMPLE #B4
Comparative Example #B4 consisted of shielding plate which was prepared
identically as the shielding plate of Example #B2 except for that the line
spacing was 150 .mu.m instead of 250 .mu.m, and no infrared blocking layer
was formed.
COMPARATIVE EXAMPLE #B5
Comparative Example #B5 consisted of shielding plate which was prepared
identically as the shielding plate of Example #B2 except for that the line
thickness was 70 .mu.m instead of 25 .mu.m, and no infrared blocking layer
was formed.
COMPARATIVE EXAMPLE #B6
Comparative Example #B6 consisted of shielding plate which was prepared
identically as the shielding plate of Example #B1 except for that
phenol-formaldehyde (Mw=50,000, n=1.73) was used as the bonding agent, and
no infrared blocking layer was formed.
COMPARATIVE EXAMPLE #B7
Comparative Example #B7 consisted of shielding plate which was prepared
identically as the shielding plate of Example #B3 except for that
polydimethylsiloxane (Mw=45,000, n=1.43) was used as the bonding agent,
and no infrared blocking layer was formed.
COMPARATIVE EXAMPLE #B8
Comparative Example #B8 consisted of shielding plate which was prepared
identically as the shielding plate of Example #B3 except for that
polyvinylidenefluoride (Mw=120,000, n=1.42) was used as the bonding agent,
and no infrared blocking layer was formed.
COMPARATIVE EXAMPLE #B9
Comparative Example #B9 consisted of shielding plate which was prepared
identically as the shielding plate of Example #B1 except for that
polyethylene film containing a filler and having a thickness of 60 .mu.m
(with a visible light transmission factor of 20% or less) was used as the
transparent plastic base member, and no infrared blocking layer was
formed.
COMPARATIVE EXAMPLE #B10
Comparative Example #B10 consisted of shielding plate which was prepared
identically as the shielding plate of Example #1 except for that the
thickness of Infrared Blocking Layer Composition #B2 was 0.05 .mu.m
instead of 5 .mu.m.
The infrared blocking ratio, EMI shielding performance, visible light
transmission factor, invisibility, bonding property before and after
heating, and fading property were actually measured, and the measured
results are summarized in Tables 3 and 4.
The infrared blocking ration was measured as an average value of the
infrared absorption ratio for the wavelength range of 900 to 1,000 nm by
using a spectrophotometer (marketed by KK Hitachi Seisakusho under the
tradename of U-3410).
The EMI shielding performance was measured by placing the specimen between
two flanges of a coaxial waveguide converter (marketed by Nihon Koshuha KK
under the tradename of TWC-S-024), and using a spectro-analyzer (marketed
by YHP under the tradename of 8510B Vector Network Analyzer) at the
frequency of 1 GHz.
The visible light transmission factor was measured as an average value of
the transmission factor over the wavelength range of 400 to 800 nm by
using a double beam spectro-photoanalyzer (marketed by KK Hitachi under
the tradename of Type 200-10).
The invisibility was measured by placing the display device at the distance
of 0.5 m, and evaluating if the geometric pattern of the electroconductive
metallic material is visible or not. The specimens were graded into "very
good", and "good" depending on the degree of invisibility, and "NG" when
the pattern was visible.
The bonding property was measured by using a tensile strength testing
machine (marketed by Toyo Baldwin KK under the tradename of Tensilon
UTM-4-100) with the width of 10 mm, 90 degree direction and peeling speed
of 50 mm/minute.
The refraction index was measured by using a refraction meter (marketed by
KK Atago Kogaku Kikai Seisakusho under the tradename of Abbe refraction
meter) at the temperature of 25.degree. C.
TABLE 3
method for 15-1a
forming transparent electro- geometric pattern
conductive plastic base conductive forming line
width line spacing line thickness
Examples layer member material pattern method (.mu.m)
(.mu.m) (.mu.m) bonding agent
#B1 foil bonding PET (50 .mu.m) Cu square chemical 25
500 18 Bonding Agent #B1
etching
(high polymer epoxy,
n = 1.57)
#B2 foil bonding PET (25 .mu.m) Al square chemical 25
250 25 Bonding Agent #B2
etching
(phenoxy resin,
n = 1.55)
#B3 drawing PET (50 .mu.m) Ni square plating 12
500 2 Bonding Agent #B3
(acrylic resin,
n = 1.47)
#B4 foil bonding PET (50 .mu.m) Cu square chemical 35
500 18 Bonding Agent #B1
etching
#B5 foil bonding PET (25 .mu.m) Al square chemical 12
250 25 Bonding Agent #B2
etching
#B6 drawing PET (50 .mu.m) Ni square plating 12
800 2 Bonding Agent #B3
#B7 foil bonding PET (50 .mu.m) Cu square chemical 25
250 18 Bonding Agent #B1
etching
#B8 foil bonding PET (25 .mu.m) Al square chemical 25
250 35 Bonding Agent #B2
etching
#B9 foil bonding PET (50 .mu.m) darkened Square chemical 25
500 18 Bonding Agent #B1
Cu etching
#B10 foil bonding PET (50 .mu.m) Cu right triangle chemical 25
500 18 Bonding Agent #B1
etching
#B11 foil bonding PET (50 .mu.m) Cu right hexagon chemical 25
500 18 Bonding Agent #B1
etching
#B12 foil bonding PET (50 .mu.m) Cu right octagon + chemical 25
500 18 Bonding Agent #B1
square etching
15-1b
optical properties
Bonding properties
Visible light
bonding force
Infrared EMI shielding transmission
initial after 80.degree. C.,
infrared blocking blocking ratio performance factor
bonding force 1,000 hrs of aging fading after 80.degree. C.,
Examples layer (%) (dB) (%)
Invisibility (kg/cm.sup.2) (kg/cm.sup.2) 1,000 hrs of aging
#B1 Composition #B1 80 50 74 good 1.2
1.2 none
#B2 Composition #B1 78 40 69 good 1.7
1.5 good
#B3 Composition #B1 80 48 70 good 0.9
0.8 none
#B4 Composition #B2 65 56 68 good 1.2
1.2 none
#B5 Composition #B2 65 38 75 good 1.7
1.6 none
#B6 Composition #B2 65 30 77 good 1.7
1.5 none
#B7 Composition #B1 80 55 70 good 1.2
1.2 none
#B8 Composition #B1 80 56 69 good 1.7
1.5 none
#B9 Composition #B2 65 48 70 very good 1.2
1.2 none
#B10 Composition #B2 65 54 69 good 1.2
1.2 none
#B11 Composition #B3 62 50 75 good 1.1
1.1 none
was directly added
to bonding layer
#B12 Composition #B3 62 48 77 good 1.1
1.1 none
was directly added
to bonding layer
TABLE 4
method for 15-2a
forming transparent electro- Geometric pattern
Comparative conductive plastic base conductive forming
Line width Line spacing line thickness
Examples layer member material pattern method
(.mu.m) (.mu.m) (.mu.m) bonding agent
#B1 vapor PET (50 .mu.m) ITO uniform -- --
0.2 Bonding Agent #B1
deposition vapor
deposition
#B2 vapor PET (25 .mu.m) Al uniform -- --
0.2 Bonding Agent #B2
deposition vapor
deposition
#B3 foil bonding PET (50 .mu.m) Cu square chemical 50
500 18 Bonding Agent #B1
etching
#B4 foil bonding PET (25 .mu.m) Al square chemical 25
150 25 Bonding Agent #B2
etching
#B5 foil bonding PET (25 .mu.m) Al square plating 25
250 70 Bonding Agent #B2
#B6 foil bonding PET (50 .mu.m) Cu square chemical 25
500 18 phenol-formaldehyde
etching
(n = 1.73)
#B7 drawing PET (50 .mu.m) Ni square plating 12
500 2 polydimethylsiloxane
(n = 1.43)
#B8 drawing PET (50 .mu.m) Ni square plating 12
500 2 polyvinylidiene
fluoride
(n = 1.42)
#B9 foil bonding polyethylene Cu square chemical 25
500 18 Bonding Agent #B1
with filler etching
(60 .mu.m)
#B10 foil bonding PET (50 .mu.m) Cu square chemical 25
500 18 Bonding Agent #B2
etching
15-2b
optical properties
bonding properties
Visible light
bonding force
Infrared EMI shielding transmission
initial after 80.degree. C.,
Comparative infrared blocking blocking ratio performance factor
bonding force 1,000 hrs of aging fading after 80.degree. C.,
Examples layer (%) (dB) (%)
invisibility (kg/cm.sup.2) (kg/cm.sup.2) 1,000 hrs of aging
#B1 -- <10 18 85 good 1.2 1.2
none
#B2 -- <10 35 <20 NG 1.7 1.5
none
#B3 -- <10 39 55 NG 1.2 1.2
none
#B4 -- <10 37 40 NG 1.7 1.5
none
#B5 -- <10 45 60 NG 0.9 0.8
none
#B6 -- <10 50 <20 -- <0.5 0.5
--
#B7 -- <10 30 <20 -- 0.9 0.9
--
#B8 -- <10 48 <20 -- <0.5 0.5
--
#B9 -- <10 50 <20 -- 1.2 1.2
none
#B10 50 .mu.m thick 29 50 80 good 1.7 1.5
none
Composition #B2
As can be appreciated from the description of the examples, the bonding
film having an electromagnetic shielding and infrared blocking property
according to the present invention can have a superior infrared blocking
capability, and can be applied very closely to the object so that a
favorable EMI shielding performance can be achieved substantially without
any electromagnetic leakage. The present invention can provide superior
bonding film which has favorable optical properties in terms of visible
light transmission factor and invisibility, and involves very little
change in the bonding properties at high temperatures over an extended
period of time. By using polyethylene-terephthalate film for the
transparent plastic member, a highly transparent, heat-resistant,
economical and easy handling bonding film having an electromagnetically
shielding and infrared blocking property can be obtained.
By using a layer of copper, aluminum or nickel having a thickness of 3 to
40 .mu.m for the electroconductive material layer, and making the surface
of the layer facing the transparent plastic base member into a coarse
surface, a highly workable and economical bonding film which has an
electromagnetically shielding and infrared blocking property can be
obtained.
By using copper having at least its outer surface darkened, a
fade-resistant and high-contrast bonding film which has an
electromagnetically shielding and infrared blocking property can be
obtained. By geometrically patterning the electroconductive material over
the transparent plastic base member with a chemical etching process, a
highly workable bonding film which has an electromagnetically shielding
and infrared blocking property can be obtained.
By using paramagnetic metal for the electroconductive material, a bonding
film having a high EMI shielding and infrared blocking property which is
effective in shielding a magnetic field can be obtained.
When this bonding film is applied to a display device and an
electromagnetic shielding assembly, a high EMI shielding effect can be
obtained, and it becomes possible to allow the display device to be viewed
as if no such bonding film were used without increasing the display
intensity by virtue of the high visible light transmission factor. Also,
it is possible to avoid any fauly operation of electronic equipment which
uses an infrared remote control such as VTR, CD and radio sets.
Furthermore, because the geometric pattern of the electroconductive
material is virtually invisible, the display device can be viewed without
any unfamiliar impression.
EXAMPLE
Bonding Film #C1
The plastic film consisted of transparent PET film having the thickness of
50 .mu.m (refraction index n=1,575). An electrolytic copper foil having
the thickness of 18 .mu.m was laminated thereover, by heating, under the
condition of 180.degree. C. and 30 kgf/cm.sup.2, via an epoxy bonding
sheet (marketed by Nikkan Kogyo KK under the tradename of Nikaflex,
n=1.58), serving as a bonding layer, with the coarse surface of the copper
foil facing the epoxy bonding sheet.
The obtained PET film laminated with copper foil is subjected to a
photo-lithographic process (including the steps of resist film coating,
photographic exposure, photographic development, chemical etching, and
resist film removal), and a copper grid pattern having the line width of
25 .mu.m and the line spacing of 500 .mu.m was formed on the surface of
the PET film to obtain Composition #C1. A bonding agent which is described
hereinafter was applied over the surface of Composition #C1 to the dry
thickness of approximately 40 .mu.m, and after a drying process, Bonding
Film #C1 having an electromagnetic shielding property and an optical
transparency was obtained. Thereafter, Bonding Film #C1 was applied over
the surface of commercially available acrylic plate (marketed by KK Kurarc
under the tradename of Komoglass, thickness 3 mm) by using a roll
laminator under the temperature and pressure condition of 110.degree. C.
and 20 kgf/cm.sup.2.
EXAMPLE
Bonding Film #C2
Aluminum foil having a thickness of 25 .mu.m was bonded over the surface of
PET film having the thickness of 25 .mu.m serving as the transparent base
material via acrylic bonding film (marketed by DuPont under the tradename
of Pyralux LF-0200, n=1.47) by using a roll laminator under the
temperature and pressure condition of 170.degree. C. and 20 kgf/cm.sup.2.
This assembly consisting of PET film laminated with aluminum foil is
subjected to a photo-lithographic process similar to that for Bonding Film
#C1, and an aluminum grid pattern having the line width of 25 .mu.m and
the line spacing of 250 .mu.m was formed on the surface of the PET film to
obtain Composition #C2. A bonding agent which is described hereinafter was
applied over the surface of Composition #C2 to the dry thickness of
approximately 30 .mu.m, and after a drying process, Bonding Film #C2
having an electromagnetic shielding property and an optical transparency
was obtained. Thereafter, Bonding Film #C2 was applied over the surface of
commercially available acrylic plate by using a thermal press under the
temperature and pressure condition of 110.degree. C., 30 kgf/cm.sup.2 and
30 minutes.
EXAMPLE
Bonding Film #C3
Electroless nickel plating serving as electroconductive material was
applied over the surface of PET film having the thickness of 50 .mu.m by
using a mask so as to form a nickel grid pattern having the line width of
12 .mu.m, the line spacing of 500 .mu.m, and the thickness of 2 .mu.m to
obtain Composition #C3. A bonding agent which is described hereinafter was
applied over the surface of Composition #C3 to the dry thickness of
approximately 70 .mu.m, and after a drying process, Bonding film #C3
having an electromagnetic shielding property and an optical transparency
was obtained. Thereafter, Bonding Film #C3 was applied over the surface of
commercially available acrylic plate by using a roll laminator under the
temperature and pressure condition of 110.degree. C., 20 kgf/cm.sup.2 and
30 minutes.
<Bonding Agent Composition #C1>
TBA-HME (Hitachi Kasei Kogyo KK; 100 weight parts
high polymer epoxy resin, Mw = 300,000)
YD-8125 (Toto Kasei Kogyo KK; 25 weight parts
bisphenol type A epoxy resin)
IPDI (Hitachi Kasei Kogyo KK; 12.5 weight parts
mask isophorone-di-isocyanate)
2-ethyl-4-methylimidazole 0.3 weight parts
MEK (methyl-ethyl-ketone) 330 weight parts
cyclohexanone 15 weight parts
The bonding agent composition was dissolved in MEK and cyclohexanone to
obtain a varnish of Bonding Agent Composition #C1. This varnish was
allowed to freely extend over the surface of a glass sheet, and the film
obtained after heating and drying had a refraction index of 1.57.
<Bonding Agent Composition #C2>
YP-30 (Toto Kasei KK, 100 weight parts
phenoxy resin, Mw = 60,000)
YD-8125 (Toto Kasei Kogyo KK; 10 weight parts
bisphenol type A epoxy resin)
IPDI (Hitachi Kasei Kogyo KK; 5 weight parts
mask-isophorone-di-isocyanate)
2-ethyl-4-methylimidazole 0.3 weight parts
MEK 285 weight parts
cyclohexanone 5 weight parts
The bonding agent composition was dissolved in MEK and cyclohexanone to
obtain a varnish of Bonding Agent Composition #C2. This varnish was
allowed to freely extend over the surface of a glass sheet, and the film
obtained after heating and drying had a refraction index of 1.55.
<Bonding Agent Composition #C3>
HTR-600LB (Teikoku Kagaku Sangyo KK, 100 weight parts
polyacrylic acid ester, Mw = 700,000)
Colonate L (Nihon Polyurethane Kogyo KK, 4.5 weight parts
3-functional isocyanate)
dibutyl-tin laurate 0.4 weight parts
toluen 450 weight parts
ethylacetate 10 weight parts
The bonding agent composition was dissolved in tolune and ethylacetate to
obtain a varnish of Bonding Agent Composition #C3. This varnish was
allowed to freely extend over the surface of a glass sheet, and the film
obtained after heating and drying had a refraction index of 1.47.
EXAMPLE #C1
Example #C1 consists of bonding film which was prepared according to the
procedure for preparing Bonding Film Composition #C1 by using Bonding
Agent Composition #C1.
EXAMPLE #C2
Example #C2 consists of bonding film which was prepared according to the
procedure for preparing Bonding Film Composition #C2 by using Bonding
Agent Composition #C2.
EXAMPLE #C3
Example #C3 consists of bonding film which was prepared according to the
procedure for preparing Bonding Film Composition #C3 by using Bonding
Agent Composition #C3.
EXAMPLE #C4
Example #C4 consists of bonding film which was identically prepared as
Example #C1 except for that the line width was 35 .mu.m instead of 25
.mu.m.
EXAMPLE #C5
Example #C5 consists of bonding film which was identically prepared as
Example #C2 except for that the line width was 12 .mu.m instead of 25
.mu.m.
EXAMPLE #C6
Example #C6 consists of bonding film which was identically prepared as
Example #C3 except for that the line spacing was 800 .mu.m instead of 500
.mu.m.
EXAMPLE #C7
Example #C7 consists of bonding film which was identically prepared as
Example #C1 except for that the line spacing was 250 .mu.m instead of 500
.mu.m.
EXAMPLE #C8
Example #C8 consists of bonding film which was identically prepared as
Example #C2 except for that the line thickness was 35 .mu.m instead of 25
.mu.m.
EXAMPLE #C9
Example #C9 consists of bonding film which was identically prepared as
Example #C1 except for that the electroconductive material consisted of
darkened copper.
EXAMPLE #C10
Example #C10 consists of bonding film which was identically prepared as
Example #C1 except for that the geometric pattern consisted of a
repetition of a right triangle instead of the grid pattern of Example #C1.
EXAMPLE #C11
Example #C11 consists of bonding film which was identically prepared as
Example #C1 except for that the geometric pattern consisted of a
repetition of a right hexagon instead of the grid pattern of Example #C1.
EXAMPLE #C12
Example #C12 consists of bonding film which was identically prepared as
Example #C1 except for that the geometric pattern consisted of a
repetition of a right octagon and a square instead of the grid pattern of
Example #C1.
COMPARATIVE EXAMPLE #C1
PET film over which ITO film was vapor deposited to the thickness of 2,000
.ANG. by vapor deposition, instead of the patterned copper foil, was used.
A bonding agent was directly applied over the assembly without
geometrically patterning the ITO film. Thereafter, bonding film was
prepared therefrom in the same way as Example #C1 to obtain Comparative
Example #C1.
COMPARATIVE EXAMPLE #C2
Transparent PET film serving as the transparent plastic base member, over
which aluminum film serving as the electroconductive material was vapor
deposited to the thickness of 2,000 .ANG., was used. Bonding Agent
Composition #C2 was directly applied over the surface of the assembly
without geometrically patterning the aluminum film. Thereafter, bonding
film was prepared therefrom in the same way as Example #C1 to obtain
Comparative Example #C2.
COMPARATIVE EXAMPLE #C3
Comparative Example #C3 consisted of bonding film which was prepared
identically as the bonding film of Example #C1 except for that the line
width was 50 .mu.m instead of 25 .mu.m.
COMPARATIVE EXAMPLE #C4
Comparative Example #C4 consisted of bonding film which was prepared
identically as the bonding film of Example #C2 except for that the line
spacing was 150 .mu.m instead of 250 .mu.m.
COMPARATIVE EXAMPLE #C5
Comparative Example #C5 consisted of bonding film which was prepared
identically as the bonding film of Example #C2 except for that the line
thickness was 70 .mu.m instead of 25 .mu.m.
COMPARATIVE EXAMPLE #C6
Comparative Example #C6 consisted of bonding film which was prepared
identically as the bonding film of Example #C1 except for that
phenol-formaldehyde (Mw=50,000, n=1.73) was used as the bonding agent.
COMPARATIVE EXAMPLE #C7
Comparative Example #C7 consisted of bonding film which was prepared
identically as the bonding film of Example #C3 except for that
polydimethylsiloxane (Mw=45,000, n=1.43) was used as the bonding agent.
COMPARATIVE EXAMPLE #C8
Comparative Example #C8 consisted of bonding film which was prepared
identically as the bonding film of Example #C3 except for that
polyvinylidenefluoride (Mw=12,000, n=1.42) was used as the bonding agent.
COMPARATIVE EXAMPLE #C9
Comparative Example #C9 consisted of bonding film which was prepared
identically as the bonding film of Example #C1 except for that
polyethylene film containing a filler and having a thickness of 60 .mu.m
(with a visible light transmission factor of 20% or less) was used as the
transparent plastic base member.
The EMI shielding performance, visible light transmission factor,
invisibility, bonding property before and after heating, and fading
property were actually measured, and the measured results are summarized
in Tables 5 and 6.
TABLE 5
method for 14-1a
forming transparent electro- geometric pattern
conductive plastic base conductive forming line
width line spacing line thickness
Examples layer member material pattern method (.mu.m)
(.mu.m) (.mu.m) bonding agent
#C1 foil bonding PET (50 .mu.m) Cu square chemical 25
500 18 Bonding Agent #C1
etching
(high polymer epoxy,
n = 1.57)
#C2 foil bonding PET (25 .mu.m) Al square chemical 25
250 25 Bonding Agent #C2
etching
(phenoxy resin,
n = 1.55)
#C3 drawing PET (50 .mu.m) Ni square plating 12
500 2 Bonding Agent #C3
(acrylic resin,
n = 1.47)
#C4 foil bonding PET (50 .mu.m) Cu square chemical 35
500 18 Bonding Agent #C1
etching
#C5 foil bonding PET (25 .mu.m) Al square chemical 12
250 25 Bonding Agent #C2
etching
#C6 drawing PET (50 .mu.m) Ni square plating 12
800 2 Bonding Agent #C3
#C7 foil bonding PET (50 .mu.m) Cu square chemical 25
250 18 Bonding Agent #C1
etching
#C8 foil bonding PET (25 .mu.m) Al square chemical 25
250 35 Bonding Agent #C2
etching
#C9 foil bonding PET (50 .mu.m) darkened square chemical 25
500 18 Bonding Agent #C1
Cu etching
#C10 foil bonding PET (50 .mu.m) Cu right triangle chemical 25
500 18 Bonding Agent #C1
etching
#C11 foil bonding PET (50 .mu.m) Cu right hexagon chemical 25
500 18 Bonding Agent #C1
etching
#C12 foil bonding PET (50 .mu.m) Cu right octagon + chemical 25
500 18 Bonding Agent #C1
square etching
14-1b
Optical properties
bonding properties
visibile light
bonding force after
HMI shielding transmission
initial bonding 80.degree. C., 1,000 hrs of fading after 80.degree. C.,
Examples (dB) factor (%)
invisibility force (kg/cm.sup.2) aging (kg/cm.sup.2) 1,000 hrs of aging
#C1 50 75 good 1.2
1.2 none
#C2 40 70 good 1.7
1.5 none
#C3 48 72 good 0.9
0.8 none
#C4 56 70 good 1.2
1.2 none
#C5 38 78 good 1.7
1.6 none
#C6 30 80 good 1.7
1.5 none
#C7 55 73 good 1.2
1.2 none
#C8 56 70 good 1.7
1.5 none
#C9 48 72 good 1.2
1.2 none
#C10 54 70 good 1.2
1.2 none
#C11 50 77 good 1.2
1.2 none
#C12 48 79 good 1.2
1.2 none
TABLE 6
method for 14-2b
forming transparent electro- geometric pattern
Comparative conductive plastic base conductive forming
line width line spacing line thickness
Examples layer member material pattern method
(.mu.m) (.mu.m) (.mu.m) bonding agent
#C1 vapor PET (50 .mu.m) ITO uniform --
-- 0.2 Bonding Agent #C1
deposition vapor
deposition
#C2 vapor PET (25 .mu.m) Al uniform --
-- 0.2 Bonding Agent #C2
deposition vapor
deposition
#C3 foil bonding PET (50 .mu.m) Cu square chemical 50
500 18 Bonding Agent #C1
etching
#C4 foil bonding PET (25 .mu.m) Al square chemical 25
150 25 Bonding Agent #C2
etching
#C5 foil bonding PET (25 .mu.m) Al square plating 25
250 70 Bonding Agent #C2
#C6 foil bonding PET (50 .mu.m) Cu square chemical 25
500 18 phenol-formaldehyde
etching
(n = 1.73)
#C7 foil bonding PET (50 .mu.m) Ni square plating 12
500 2 polydimethylsiloxane
(n = 1.43)
#C8 drawing PET (50 .mu.m) Ni square plating 12
500 2 polyvinylidiene
fluoride
(n = 1.43)
#C9 foil bonding polyethylene Cu square chemical 25
500 18 Bonding Agent #C1
with filler etching
(60 .mu.m)
14-2b
optical properties
4 visible light
bonding properties
transmission
bonding force after
Comparative EMI shielding factor
initial bonding 80.degree. C., 1,000 hrs of fading after 80.degree. C.,
Examples (dB) (%)
invisibility force (kg/cm.sup.2) aging (kg/cm.sup.2) 1,000 hrs of aging
#C1 18 83 good 1.2
1.2 none
#C2 35 <20 NG 1.7
1.5 none
#C3 39 55 NG 1.2
1.2 none
#C4 37 40 NG 1.7
1.5 none
#C5 45 60 NG 0.9
0.8 none
#C6 50 <20 -- <0.5 0.5
--
#C7 30 <20 -- 0.9 0.9
--
#C8 48 <20 -- <0.5 0.3
--
#C9 50 <20 -- 1.2 1.2
none
The EMI shielding performance was measured by placing the specimen between
two flanges of a coaxial waveguide converter (marketed by Nihon Koshuha KK
under the tradename of TWC-S-024), and using a spectro-analyzer (marketed
by YHP under the tradename of 8510B Vector Network Analyzer) at the
frequency of 1 GHz.
The visible light transmission factor was measured as an average value of
the transmission factor over the wavelength range of 400 to 800 nm by
using a double beam spectro-photoanalyzer (marketed by KK Hitachi under
the tradename of Type 200-10).
The invisibility was measured by placing the display device at the distance
of 0.5 m, evaluating if the geometric pattern of the electroconductive
metallic material is visible or not. The specimens were graded into "very
good", and "good" depending on the degree of invisibility, and "NG" when
the pattern was visible.
The bonding property was measured by using a tensile strength testing
machine (marketed by Toyo Baldwin KK under the tradename of Tensilon
UTM-4-100) with the width of 10 nm, 90 degree direction and peeling speed
of 50 mm/minute.
The refraction index was measured by using a refraction meter (marketed by
KK Atago Kogaku Kikai Seisakusho under the tradename of Abbe refraction
meter) at the temperature of 25.degree. C.
As can be appreciated from the description of the examples, the bonding
film having an electromagnetic shielding and optically transparent
property according to the present invention can be applied very closely to
the object so that a favorable EMI shielding performance can be achieved
substantially without any electromagnetic leakage. The present invention
can provide superior bonding film which has favorable optical properties
in terms of visible light transmission factor and invisibility, and
involves very little change in the bonding properties at high temperatures
over an extended period of time. By using polyethylene-terephthalate film
for the transparent plastic member, a highly transparent, heat-resistant,
economical and easy handling bonding film having an electromagnetically
shielding and optically transparent property can be obtained.
By using a layer of copper, aluminum or nickel having a thickness of 3 to
40 .mu.m for the electroconductive material layer, and making the surface
of the layer facing the transparent plastic base member into a coarse
surface, a highly workable and economical bonding film which has an
electromagnetically shielding and optically transparent property can be
obtained.
By using copper having at least its outer surface darkened, a
fade-resistant and high-contrast bonding film which has an
electromagnetically shielding and optically transparent property can be
obtained. By geometrically patterning the electroconductive material over
the transparent plastic base member with a chemical etching process, a
highly workable bonding film which has an electromagnetically shielding
and optically transparent property can be obtained.
By using paramagnetic metal for the electroconductive material, a bonding
film having a high EMI shielding and infrared blocking property which is
effective in shielding a magnetic field can be obtained.
When this bonding film is applied to a display device and an
electromagnetic shielding assembly, a high EMI shielding effect can be
obtained, and it becomes possible to allow the display device to be viewed
as if no such bonding film were used without increasing the display
intensity by virtue of the high visible light transmission factor.
Furthermore, because the geometric pattern of the electroconductive
material is virtually invisible, the display device can be viewed without
any unfamiliar impression.
EXAMPLE
Bonding Film #D1
The transparent plastic base sheet consisted of transparent PET film having
the thickness of 50 .mu.m (refraction index n=1,575). An electrolytic
copper foil having the thickness of 12 .mu.m was laminated thereover, by
heating, under the condition of 180.degree. C. and 30 kgf/cm.sup.2, via an
epoxy bonding film (marketed by Nikkan Kogyo KK under the tradename of
Nikaflex, n=1.58), serving as a bonding layer, with the coarse surface of
the copper foil facing the epoxy bonding film.
The obtained PET film laminated with copper foil is subjected to a
photo-lithographic process (including the steps of resist film coating,
photographic exposure, photographic development, chemical etching, and
resist film removal), and a copper grid pattern having the line width 25
.mu.m and the line spacing of 1 mm was formed on the surface of the PET
film to obtain Composition #D1. The visible light transmission factor of
Composition #D1 was 20% or less. A bonding agent which is described
hereinafter was applied over the surface of Composition #D1 to the dry
thickness of approximately 20 .mu.m, and after a drying process, Bonding
Film #D1 was obtained. Thereafter, a pair commercially available acrylic
plates (marketed by KK Kurare under the tradename of Komoglass, thickness
1 mm) were laminated over either side of Bonding Film #D1 by using a roll
laminator under the temperature and pressure condition of 110.degree. C.
and 20 kgf/cm.sup.2 to obtain electromagnetic shielding material.
EXAMPLE
Bonding Film #D2
Copper foil having the thickness of 12 .mu.m was bonded over the surface of
PET film having the thickness of 25 .mu.m serving as the transparent base
material via acrylic bonding film (marketed by DuPont under the tradename
of Pyralux LF-0200, n=1.47, thickness 20 .mu.m). This assembly consisting
of PET film laminated with copper foil is subjected to a
photo-lithographic process similar to that for Bonding Film #D1, and an
copper grid pattern having the line width of 15 .mu.m and the line spacing
of 2.0 mm was formed on the surface of the PET film to obtain Composition
#D2. The visible light transmission factor of Composition #D2 was 20% or
less. A bonding agent which is described hereinafter was applied over the
surface of Composition #D2 carrying the geometric pattern to the dry
thickness of approximately 30 .mu.m, and was dried. Then, the bonding
agent which is described hereinafter was applied to the other surface of
the Composition #D2 to the dry thickness of approximately 20 .mu.m to
obtain Bonding Film #D2. Thereafter, a pair of commercially available
acrylic plates (marketed by KK Kurare under the tradename of Komoglass,
thickness 1.5 mm) were laminated over either side of Bonding Film #D2 by
using a press under the temperature and pressure condition of 110.degree.
C. and 30 kgf/cm.sup.2 to obtain electromagnetic shielding material.
EXAMPLE
Bonding Film #D3
Electroless nickel plating was applied over the surface of PET film having
the thickness of 50 .mu.m by using a mask so as to form a nickel grid
pattern having the line width of 10 .mu.m, the line spacing of 1.0 mm, and
the thickness of 30 .mu.m to obtain a Composition #D3. The visible light
transmission factor of Composition #D3 was 20% or less. A bonding agent
which is described hereinafter was applied over the surface of Composition
#D3 carrying the geometrically patterned nickel layer to the dry thickness
of approximately 30 .mu.m, and was dried. Then, the bonding agent which is
described hereinafter was applied to the other surface of the Composition
#D2 to the dry thickness of approximately 20 .mu.m to obtain Bonding Film
#D3. Thereafter, a pair of commercially available acrylic plates (marketed
by KK Kurare under the tradename of Komoglass, thickness 1.5 mm) were
laminated over either side of Bonding Film #D3 by using a press under the
temperature and pressure condition of 110.degree. C. and 20 kgf/cm.sup.2
to obtain electromagnetic shielding material.
<Bonding Agent Composition #D1>
TBA-HME (Hitachi Kasei Kogyo KK; 100 weight parts
high polymer epoxy resin, Mw = 300,000)
YD-8125 (Toto Kasei Kogyo KK; 25 weight parts
bisphenol type A epoxy resin)
IPDI (Hitachi Kasei Kogyo KK; 12.5 weight parts
mask isophorone-di-isocyanate)
2-ethyl-4-methylimidazole 0.3 weight parts
MEK (methyl-ethyl-ketone) 330 weight parts
cyclohexanone 15 weight parts
The refraction index of Bonding Agent Composition #D1 after drying the
solvents was 1.57.
<Bonding Agent Composition #D2>
YP-30 (Toto Kasei KK, 100 weight parts
phenoxy resin, Mw = 60,000)
YD-8125 (Toto Kasci Kogyo KK; 10 weight parts
bisphenol type A epoxy resin)
IPDI (Hitachi Kasei Kogyo KK; 5 weight parts
mask-isophorone-di-isocyanate)
2-ethyl-4-methylimidazol 0.3 weight parts
MEK 285 weight parts
cyclohexanone 5 weight parts
The refraction index of Bonding Agent Composition #D2 after drying the
solvents was 1.55.
<Bonding Agent Composition #D3>
HTR-600LB (Teikoku Kagaku Sangyo KK, 100 weight parts
polyacrylic acid ester, Mw = 700,000)
Colonate L (Nihon Polyurethane Kogyo KK, 4.5 weight parts
3-functional isocyanate)
dibutyl-tin laurate 0.4 weight parts
toluen 450 weight parts
ethylacetate 10 weight parts
The refraction index of Bonding Agent Composition #D2 after drying the
solvents was 1.47.
Example #D1
Example #D1 consists of electromagnetic shielding material which was
prepared according to the procedure for preparing Bonding Film #D1 by
using Bonding Agent Composition #D1.
Example #D2
Example #D2 consists of electromagnetic shielding material which was
prepared according to the procedure for preparing Bonding Film #D2 by
using Bonding Agent Composition #D2.
Example #D3
Example #D3 consists of electromagnetic shielding material which was
prepared according to the procedure for preparing Bonding Film #D3 by
using Bonding Agent Composition #D3.
Example #D4
Example #D4 consists of electromagnetic shielding material which was
identically prepared as Example #D1 except for that the line width was 9
.mu.m instead of 20 .mu.m.
Example #D5
Example #D5 consists of electromagnetic shielding material which was
identically prepared as Example #D2 except for that the line width was 12
.mu.m instead of 15 .mu.m.
Example #D6
Example #D6 consists of electromagnetic shielding material which was
identically prepared as Example #D3 except for that the line spacing was
0.5 .mu.m instead of 1.0 mm.
Example #D7
Example #D7 consists of electromagnetic shielding material which was
identically prepared as Example #D1 except for that the line spacing was
5.0 mm instead of 1.0 mm.
Example #D8
Example #D8 consists of electromagnetic shielding material which was
identically prepared as Example #D2 except for that the line thickness was
18 .mu.m instead of 12 .mu.m.
Example #D9
Example #D9 consists of electromagnetic shielding material which was
identically prepared as Example #D1 except for that the electroconductive
material consists of darkened copper.
Example #D10
Example #D10 consists of electromagnetic shielding material which was
identically prepared as Example #D1 except for that the geometric pattern
of copper foil consists of a repetition of a right triangle instead of the
grid pattern of Example #D1.
Example #D11
Example #D11 consists of electromagnetic shielding material which was
identically prepared as Example #D2 except for that the geometric pattern
consisted of a repetition of a right hexagon instead of the copper grid
pattern of Example #D2.
Example #D12
Example #D12 consists of electromagnetic shielding material which was
identically prepared as Example #D3 except for that the geometric pattern
consisted of a repetition of a right octagon and a square instead of the
nickel grid pattern of Example #D3.
Example #D13
Example #D13 consists of electromagnetic shielding material which was
identically prepared as Example #D1 except for that the plastic base
member consisted of polysulfone (50 .mu.m, n=1.633) instead of PET.
Comparative Example #D1
PET film over which ITO film was vapor depositioned to the thickness of
2,000 .ANG. by vapor deposition, instead of the patterned copper foil, was
used. Bonding Agent Composition #D1 was directly applied over the two
sides of the assembly without geometrically patterning the ITO film.
Thereafter, electromagnetic shielding material was prepared therefrom in
the same way as Example #D1 to obtain Comparative Example #D1.
Comparative Example #D2
Transparent PET film having aluminum film entirely vapor deposited on one
surface thereof was used without any geometric patterning. Bonding Agent
Composition #D2 was directly applied over the two sides of the assembly.
Thereafter, electromagnetic shielding material was prepared therefrom in
the same way as Example #D1 to obtain Comparative Example #D2.
Comparative Example #D3
Comparative Example #D3 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #D1 except for that the line width was 50 .mu.m instead of 20
.mu.m.
Comparative Example #D4
Comparative Example #D4 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #D2 except for that the line spacing was 0.25 mm instead of 2.0
mm.
Comparative Example #D5
Comparative Example #D5 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #D2 except for that the line thickness was 70 .mu.m instead of
12 .mu.m.
Comparative Example #D6
Comparative Example #D6 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #D2 except for that polyethylene film containing a filler (with
a visible transmission factor of 20% or less) was used for the transparent
plastic film.
Comparative Example #D7
An assembly was prepared by applying Bonding Agent Composition #D1 only on
the surface of the Composition #D1 carrying the electroconductive material
according to the procedure for preparing Example 1 to the dry thickness of
30 .mu.m, and, after drying Bonding Agent Composition #D1, was attached to
an acrylic plate having the thickness of 2.0 mm instead of the acrylic
plate of Example #D1.
Comparative Example #D8
A pair of acrylic plates were used instead of the acrylic plates of Example
2, and the thickness of the upper plate was 1.5 mm while that of the lower
plate was 1.0 mm.
Reference Example #D1
Reference Example #D1 consisted of electromagnetic shielding material which
was prepared identically as the electromagnetic shielding material of
Example #D1 except for that phenol-formaldehyde resin (Mw=50,000, n=1.73)
was used as the bonding agent.
Reference Example #D2
Reference Example #D2 consisted of electromagnetic shielding material which
was prepared identically as the electromagnetic shielding material of
Example #D3 except for that polydimethylsiloxane (Mw=45,000, n=1.43) was
used as the bonding agent.
Reference Example #D3
Reference Example #D3 consisted of electromagnetic shielding material which
was prepared identically as the electromagnetic shielding material of
Example #D3 except for that polyvinylidenefluoride (Mw=120,000, n=1.42)
was used as the bonding agent.
The EMI shielding performance, visible light transmission factor,
warp-resistance, invisibility, optical distortion, bonding property before
and after heating, and fading property of the thus obtained
electromagnetic shielding material were actually measured, and the
measured results are summarized in Tables 7 and 8.
The EMI shielding performance was measured by placing the specimen between
two flanges of a coaxial waveguide converter (marketed by Nihon Koshuha KK
under the tradename of TWC-S-024), and using a spectro-analyzer (marketed
by YHP under the tradename of 8510B Vector Network Analyzer) at the
frequency of 1 GHz.
The visible light transmission factor was measured as an average value of
the transmission factor over the wavelength range of 400 to 800 nm by
using a double beam spectro-photoanalyzer (marketed by KK Hitachi under
the tradename of Type 200-10).
The invisibility and optical distortion were measured by placing the
display device at the distance of 0.5 m, and evaluating if the geometric
pattern of the electroconductive metallic material is visible or not, and
if the image is distorted or not. The specimens were graded into "very
good", and "good" depending on the degree of invisibility, and "NG" when
the pattern was visible, and into "NG" and "good" depending on the
presence of any detectable image distortion.
The bonding property was measured by using a tensile strength testing
machine (marketed by Toyo Baldwin KK under the tradename of Tensilon
UTM-4-100) with the width of 10 mm, 90 degree direction and peeling speed
of 50 mm/minute.
The refraction index was measured by using a refraction meter (marketed by
KK Atago Kogaku Kikai Seisakusho under the tradename of Abbe refraction
meter) at the temperature of 25.degree. C.
TABLE 7
Examples
items #D1 #D2 #D3 #D4 #D5 #D6 #D7 #D8 #D9 #D10 #D11 #D12 #D13
method of forming foil foil drawing foil foil drawing foil
foil foil foil foil drawing foil
conductive layer bonding bonding bonding bonding bonding
bonding bonding bonding bonding bonding
conductive material Cu Cu Ni Cu Cu Ni Cu
Cu darkened Cu Cu NI Cu
Cu
plastic film PET PET PET PET PET PET PET
PET PET PET PET PET poly-
sulfone
shape square square square square square square square
square square right right octagon + square
triangle hexagon square
patterning CE CE M CE CE M CE CE
CE CE CE M CE
method *1
line width (.mu.m) 20 15 10 9 12 10 20
15 20 20 15 10 20
line spacing (.mu.m) 1000 2000 1000 1000 2000 500 5000
2000 1000 1000 2000 1000 1000
line thickness (.mu.m) 12 12 3 12 12 3 12
18 12 12 12 3 12
bonding agent 1 2 3 1 2 3 1 2
1 1 2 3 1
composition *2
EMI shielding 40 35 40 38 33 44 33 35
40 41 39 38 40
performance
visible light 74 75 72 70 75 68 70 74
74 70 76 72 66
transmission factor
(%)
invisibility good good good good good good good
good very good good good good
good
view clarity good good good good good good good
good good good good good good
warping (mm) none none none none none none none
none none none none none none
initial bonding force 1.2 1.7 0.9 1.2 1.7 0.9 1.2
1.7 1.2 1.2 1.7 0.9 1.2
(kgf/cm.sup.2)
bonding force after 1.2 1.5 0.8 1.2 1.6 0.8 1.2
1.5 1.2 1.2 1.4 0.7 1.2
80.degree. C.-
1,000 hrs of aging
*1 CE: chemical deposition, M: plating
*2 #D1: Bonding Agent Composition #D1, #D2: Bonding Agent Composition #D2,
and #D3: Bonding Agent Composition #D3.
TABLE 8
Reference Examples
Comparative Examples
items #D1 #D2 #D3 #D4 #D5 #D6 #D7 #D8 #D1 #D2
#D3
method of forming vapor vapor foil foil foil foil
foil foil foil drawing drawing
conductive layer deposition deposition bonding bonding bonding bonding
bonding bonding bonding
conductive material ITO Al Cu Cu Cu Cu
Cu Cu Cu Ni Ni
plastic film PET PET PET PET PET PE with
PET PET PET PET PET
filler
shape entire entire square square square square
square square square square square
surface surface
patterning method *1 -- -- CE CE CE CE CE CE
CE M M
line width (.mu.m) -- -- 50 15 15 20 20 15
20 10 10
line spacing (.mu.m) -- -- 1000 250 2000 1000 1000 2000
1000 1000 1000
line thickness (.mu.m) 0.2 0.2 12 12 70 12
12 12 12 3 3
bonding agent 1 2 1 2 2 1 1
2 phenol- poly- polyvinyl-
composition *2
formaldehyde dimethyl- idiene-
siloxane fluoride
emi shielding performance 18 35 43 50 35 40
40 35 40 40 40
visible light 85 20> 65 40 73 20> 72
75 20> 20> 20>
transmissivity (%)
invisibility good NG NG NG NG good
good good -- -- --
? good good NG NG NG NG good
good NG NG NG
? none none none none none none large
large none none none
initial bonding force 1.2 1.7 1.2 1.7 1.6 1.2
1.2 1.7 0.5> 0.9 0.5>
(kgf/cm.sup.2)
bonding force after 80.degree. C.- 1.2 1.5 1.2 1.5 1.5
1.2 1.2 1.5 0.5 0.9 0.5
1,000 hrs of aging
*1 CE: chemical deposition, M: plating
*2 #D1: Bonding Agent Composition #D1, #D2: Bonding Agent Composition #D2,
and #D3: Bonding Agent Composition #D3.
Comparative Examples #D1 and #D2 used vapor deposited ITO and Al,
respectively, as the electroconductive material. ITO lacks a favorable
electromagnetic shielding property, and Al lacks a favorable visible light
transmission factor. Comparative Example #D3 lacked a favorable visible
light transmission factor and invisibility because the line width was 50
.mu.which is substantially larger than the upper limit of 25 .mu.m which
is required by the present invention. Similarly as Comparative Example
#D3, Comparative Example #D4 lacked a favorable visible light transmission
factor and invisibility because the line spacing was 250 .mu.m which is
substantially narrower than the lower limit of 500 .mu.m which is required
by the present invention. Comparative Example #D5 lacked a favorable
invisibility because the line thickness was 70 .mu.m which is
substantially larger than the upper limit of 18 .mu.m which is required by
the present invention. Comparative Example #D6 had a poor visible light
transmission factor of 20% or less because fairly opaque polyethylene film
containing a filler (having a visible light transmission factor of 20% or
less) was used instead of the transparent plastic film. Comparative
Example #D7 had an undesired tendency to warp because the transparent
plastic film was attached only to one side of the transparent plastic base
sheet instead of attaching a pair of transparent plastic base sheet onto
either side of the transparent plastic film each via a bonding agent
layer. Comparative Example #D8 had an undesired tendency to warp because a
pair of transparent plastic base sheets having unequal thicknesses were
attached to either side of the transparent plastic film each via a bonding
agent layer. On the other hand, the electromagnetic shielding material of
Examples #D1 to #D13 according to the present invention features a pair of
transparent plastic base sheets attached to either side of the transparent
plastic film each via a bonding agent layer and has a favorable
electromagnetic shielding performance of 33 dB or more. According to the
present invention, the visible transmission factor is 66% or better, and a
favorable invisibility can be achieved. Also, the initial bonding force is
large and the bonding force drops very little even after 1,000 hours of
aging test at 80.degree. C. Also, the electromagnetic shielding material
according to the present invention does not tend to warp. If the
difference in refraction index between the bonding agent and the
transparent plastic film or between the two bonding agents exceeds 0.14 as
was the case with Reference Examples #D1 to #D3.
As can be appreciated from the description of the examples, the
electromagnetic shielding material according to the present invention can
have a high electromagnetic shielding property, free from leakage of
electromagnetic radiation, and favorable optical properties in terms of
visible light transmission factor, invisibility, and absence of
distortion. It also is free from warping, and involves very little change
in the optical properties at high temperatures over an extended period of
time. By using polyethylene-terephthalate film for the transparent plastic
film, a highly transparent, heat-resistant, economical and easy handling
electromagnetic shielding material can be obtained.
By using a layer of copper, aluminum or nickel having a thickness of 3 to
18 .mu.m for the electroconductive material layer, a highly workable and
economical electromagnetic shielding material which additionally provides
a wide viewing angle can be obtained.
By using copper having at least its outer surface darkened, a
fade-resistant and high-contrast electromagnetic shielding material can be
obtained. By geometrically patterning the electroconductive material over
the transparent plastic base member with a chemical etching process, a
highly workable electromagnetic shielding material can be obtained.
By using paramagnetic metal for the electroconductive material, a
electromagnetic shielding material which is effective in shielding a
magnetic field can be obtained. By using PMMA for the transparent plastic
base sheet, a highly transparent and workable electromagnetic shielding
material can be obtained. By selecting the materials such that the
difference in refraction index between the transparent plastic base sheet
and the bonding layer is 0.14 or less, a highly transparent
electromagnetic shielding material can be obtained. When this
electromagnetic shielding material is applied to a display device, a high
EMI shielding effect can be obtained, and it becomes possible to allow the
display device to be viewed comfortably with a high visible light
transmission factor and a favorable invisibility.
<Surface Processed Film #E1>
ZrO.sub.2 was vacuum deposited with the electron beam heating method, under
the vacuum condition of 1 to 2.times.10.sup.-4 Torr, onto the surface of
polyethylene-terephthalate (PET) film having the thickness of 50 .mu.m and
the refraction index of 1.575, and ZrO.sub.2 thin film having the
thickness of approximately 650 .ANG. and the refraction index of 2.05 was
obtained. Additionally, SiO.sub.4 thin film having the thickness of
approximately 940 .ANG. and the refraction index of 1.46 was formed over
the ZrO.sub.2 thin film with the electron beam heating method under the
same condition to obtain Surface Processed Film #E1.
<Surface Processed Film #E2>
A bonding composition, consisting of 100 weight parts of YP-30 (marketed by
Toto Kasei KK, Mw=60,000) consisting of phenoxy resin, 10 weight parts of
YD-8125 (marketed by Toto Kasei Kogyo KK) consisting of bisphenol type A
epoxy resin, 5 weight parts of IPDI (marketed by Hitachi Kasei Kogyo KK,
mask-iisophronone-di-isocyanate; mask-isocyanate), 0.3 weight parts of a
curing promoting agent consisting of 2-ethyl-4-methylimidazole, and 285
weight parts of methylethylketone (MEK) serving as a solvent, was mixed
well with 20 weight parts of MEK dispersed coloidal silicasol (marketed by
Nissan Kagaku Kogyo KK) and 0.05 weight parts of a silicone surface
reactant by using a homogenizer. This composition was applied over the
surface of transparent PET film having the thickness of 25 .mu.m to the
dry thickness of 2 .mu.m by using an applicator to obtain Surface
Processed Film #E2.
<Electromagnetic Shielding Film #E1>
By using Surface Processed Film #E1 for the transparent plastic film, an
electrolytic copper foil having the thickness of 12 .mu.m was laminated
the transparent plastic film, by heating, under the condition of
180.degree. C. and 30 kgf/cm.sup.2, via an epoxy film (marketed by Nikkan
Kogyo KK under the tradename of Nikaflex, n=1.58, thickness 20 .mu.m),
serving as a bonding layer, with the coarse surface of the copper foil
facing the epoxy bonding film under the temperature and pressure condition
of 180.degree. C. and 30 kgf/cm.sup.2. The obtained PET film laminated
with copper foil is subjected to a photo-lithographic process (including
the steps of resist film coating, photographic exposure, photographic
development, chemical etching, and resist film removal), and a copper grid
pattern having the line width of 20 .mu.m and the line spacing of 1.0 mm
was formed on the surface of the PET film to obtain Electromagnetic
Shielding Film #E1.
<Electromagnetic Shielding Film #E2>
By using Surface Processed Film #E2 for the transparent plastic film,
copper foil having the thickness of 12 .mu.m was bonded over the surface
of the transparent plastic film via acrylic bonding film (marketed by
DuPont under the tradename of Pyralux LF-0200, n=1.47, thickness 20
.mu.m). This assembly consisting of PET film laminated with copper foil is
subjected to a photo-lithographic process similar to that for
Electromagnetic Shielding Film #E1, and an copper grid pattern having the
line width of 15 .mu.m and the line spacing of 2.0 mm was formed on the
surface of the PET film to obtain Electromagnetic Shielding Film #E2.
<Electromagnetic Shielding Film #E3>
By using Surface Processed Film #E2 for the transparent plastic film,
electroless nickel plating was applied over the surface of the transparent
plastic film by using a mask so as to form a nickel grid pattern having
the line width of 10 .mu.m, the line spacing of 1.0 mm, and the thickness
of 3 .mu.m to obtain Electromagnetic Shielding Film #E3
<Electromagnetic Shielding Film #E4>
The geometrically electroconductive material formed on Electromagnetic
Shielding Film #E1 was covered by a bonding agent composition which is
described hereinafter to the dry thickness of 30 .mu.m.
#<Bonding Agent Composition #E1>
TBA-HME (Hitachi Kasei Kogyo KK; 100 weight parts
high polymer epoxy resin, Mw = 300,000)
YD-8125 (Toto Kasei Kogyo KK; 25 weight parts
bisphenol type A epoxy resin)
IPDI (Hitachi Kasei Kogyo KK; 12.5 weight parts
mask-isocyanate)
2-ethyl-4-methylimidazole 0.3 weight parts
MEK (methyl-ethyl-ketone) 330 weight parts
cyclohexanone 15 weight parts
The refraction index of Bonding Agent Composition #E1 after drying the
solvents was 1.57.
<Bonding Agent Composition #E2>
YP-30 (Toto Kasei KK, 100 weight parts
phenoxy resin, Mw = 60,000)
YD-8125 (Toto Kasei Kogyo KK; 10 weight parts
bisphenol type A epoxy rcsin) 10 weight parts
IPDI (Hitachi Kasei Kogyo KK; 5 weight parts
mask-isophorone-di-isocyanate)
2-ethyl-4-methylimidazole 0.3 weight parts
MEK 285 weight parts
cyclohexanonc 5 weight parts
The refraction index of Bonding Agent Composition #E2 after drying the
solvents was 1.55.
<Bonding Agent Composition #E3>
HTR-600LB (Teikoku Kagaku Sangyo KK, 100 weight parts
polyacrylic acid ester, Mw = 700,000)
Colonate L (Nihon Polyurethane Kogyo KK, 4.5 weight parts
3-functional isocyanate)
dibutyl-tin laurate 0.4 weight parts
toluen 450 weight parts
ethylacetate 10 weight parts
The refraction index of Bonding Agent Composition #E2 after drying the
solvents was 1.47.
<Infrared Blocking Layer Composition #E1>
YD-8125 (Toto Kasei Kogyo KK; 100 weight parts
bisphenol type A epoxy resin)
copper (II) sulfide (Wako Junyaku KK, crushed 4 weight parts
to an average particle diameter of 0.5 .mu.m
by using a Henschel mixer)
2-ethyl-3-methylimidazol 0.5 weight parts
dicyandiamide 5 weight parts
MEK 200 weight parts
etyleneglycol-monomethyether 20 weight parts
The compound was applied with an applicator at room temperature, and was
cured by heating at 90.degree. C. for 30 minutes.
Infrared Blocking Layer Composition #E2>
HTR-280 (Teikoku Kagaku Sangyo KK, 100 weight parts
polyacrylic acid ester copolymer, Mw = 700,000)
UFP-HX (Sumitomo Kinzoku Kozan KK, 0.5 weight parts
ITO, verage particle diameter 0.1 .mu.m)
Colonate L (Nihon Polyurethane Kogyo KK, 5 weight parts
3-functional isocyanate)
dibutyl-tin laurate 0.4 weight parts
toluen 450 weight parts
ethylacetate 10 weight parts
The compound was applied with an applicator at room temperature, and was
cured by heating at 90.degree. C. for 30 minutes.
<Infrared Blocking Layer Composition #E3>
YP-30 (Toto Kasei KK, 100 weight parts
phenoxy resin, Mw = 60,000)
YD-8125 (Toto Kasei Kogyo KK; 10 weight parts
bisphenol type A epoxy resin)
IPDI (Hitachi Kasei Kogyo KK; 5 weight parts
mask-isocyanate)
MEK 285 weight parts
IRG-022 (Nihon Kayaku KK, 1 weight part
aromatic di-imonium salt)
The compound was applied with an applicator at room temperature, and was
cured by heating at 90.degree. C. for 30 minutes.
Example #E1
Electromagnetic Shielding Film #E1 and the bonding film obtained by
applying Bonding Agent Composition #E1 over the surface of transparent PET
film having the thickness of 50 .mu.m to the dry thickness of
approximately 20 .mu.m and drying the assembly were bonded over two sides
of a commercially available acrylic plate (marketed by KK Kurare under the
tradename of Komoglass, thickness 1 mm) by using a roll laminator under
the temperature and pressure condition of 110.degree. C. and 20
kgf/cm.sup.2 to obtain electromagnetic shielding material of Example #E1.
Example #E2
Electromagnetic Shielding Film #E2 and the bonding film obtained by
applying Bonding Agent Composition #E2 over the surface of transparent PET
film having the thickness of 50 .mu.m to the dry thickness of
approximately 20 .mu.m and drying the assembly were bonded over two sides
of a commercially available acrylic plate (marketed by KK Kurare under the
tradename of Komoglass, thickness 1 mm) by using a roll laminator under
the temperature and pressure condition of 110.degree. C. and 10
kgf/cm.sup.2 to obtain electromagnetic shielding material of Example #E2.
Example #E3
Example #E3 consisted of electromagnetic shielding material which was
prepared in the same way as Example #E1 except for that Electromagnetic
Shielding Film #E3 was used.
Example #E4
Electromagnetic Shielding Film #E4 covered by Bonding Agent Composition #E3
and the bonding film obtained by applying Bonding Agent Composition #E3
over the surface of transparent PET film having the thickness of 50 .mu.m
to the dry thickness of approximately 20 .mu.m and drying the assembly
were bonded over two sides of a commercially available acrylic plate
(marketed by KK Kurare under the tradename of Komoglass, thickness 1 mm)
by using roll laminator under the temperature and pressure condition of
110.degree. C. and 20 kgf/cm.sup.2 to obtain electromagnetic shielding
material of Example #E4.
Example #E5
Example #E5 consists of electromagnetic shielding material which was
identically prepared as Example #E1 except for that the line width was 12
.mu.m instead of 20 .mu.m.
Example #E6
Example #E6 consists of electromagnetic shielding material which was
identically prepared as Example #E2 except for that the line spacing was
0.5 mm instead of 2.0 mm.
Example #E7
Example #E7 consists of electromagnetic shielding material which was
identically prepared as Example #E4 except for that the line spacing was
5.0 mm instead of 1.0 mm.
Example #E8
Example #E8 consists of electromagnetic shielding material which was
identically prepared as Example #E2 except for that the line thickness was
18 .mu.m instead of 12 .mu.m.
Example #E9
Example #E9 consists of electromagnetic shielding material which was
identically prepared as Example #E1 except for that the electroconductive
material consisted of darkened copper.
Example #E10
Example #E10 consists of electromagnetic shielding material which was
identically prepared as Example #E1 except for that the geometric pattern
of copper foil consisted of a repetition of a right triangle instead of
the grid pattern of Example #E1.
Example #E11
Example #E11 consists of electromagnetic shielding material which was
identically prepared as Example #E2 except for that the geometric pattern
consisted of a repetition of a right hexagon instead of the grid pattern
of Example #E2.
Example #E12
Example #E12 consists of electromagnetic shielding material which was
identically prepared as Example #E3 except for that the geometric pattern
consisted of a repetition of a right octagon and a square instead of the
grid pattern of Example #E3.
Example #E13
Example #E13 consists of electromagnetic shielding material which was
identically prepared as Example #E1 except for that the plastic base
number consisted of polysulfone (50 .mu.m) instead of PET.
Example #E14
Electromagnetic Shielding Film #E1 and the bonding film obtained by
applying Infrared Blocking Layer Composition #E1 over the surface of
transparent PET film having the thickness of 50 .mu.m to the dry thickness
of approximately 20 .mu.m and drying the assembly were bonded over two
sides of a commercially available acrylic plate (marketed by KK Kurare
under the tradename of Komoglass, thickness 1 mm) by using a roll
laminator under the temperature and pressure condition of 110.degree. C.
and 20 kgf/cm.sup.2 to obtain electromagnetic shielding material of
Example #E14.
Example #E15
Example #E15 consists of electromagnetic shielding material which is
identically prepared as Example #E14 except for that Infrared Blocking
Layer Composition #E2 was used.
Example #E16
Example #E15 consists of electromagnetic shielding material which was
identically prepared as Example #E14 except for that Infrared Blocking
Layer Composition #E3 was used.
Comparative Example #E1
ITO film was vapor deposited on the unprocessed surface of the transparent
plastic film (thickness 50 .mu.m) consisting of Surface Processed Film #E1
to the thickness of 2,000 .ANG. by vapor deposition without geometric
patterning. Bonding Agent Composition #E1 was directly applied over the
vapor deposited side of the assembly to the dry thickness of 20 .mu.m.
Similarly as Example #E1, this assembly and the bonding film obtained by
applying Bonding Agent Composition #E1 over the surface of transparent PET
film having the thickness of 50 .mu.m to the dry thickness of
approximately 20 .mu.m and drying the assembly were bonded over two sides
of a commercially available acrylic plate (marketed by KK Kurare under the
tradename of Komoglass, thickness 1 mm) under the temperature and pressure
condition of 110.degree. C. and 10 kgf/cm.sup.2 to obtain electromagnetic
shielding material of Comparative Example #E1.
Comparative Example #E2
Comparative Example #E2 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #E1 except for that aluminum, instead of ITO, was deposited on
the entire surface of the assembly, and Bonding Agent Composition #E2 was
directly applied.
Comparative Example #E3
Comparative Example #E3 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #E1 except for that the line width was 50 .mu.m instead of 20
.mu.m.
Comparative Example #E4
Comparative Example #E4 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #E2 except for that the line spacing was 0.25 mm instead of 2.0
mm.
Comparative Example #E5
Comparative Example #E5 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #E2 except for that the line thickness was 70 .mu.m instead of
12 .mu.m.
Comparative Example #E6
Comparative Example #E6 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #E1 except for that phenol-formaldehyde resin (Mw=50,000,
n=1.73) was used instead of Bonding Agent Composition #E1.
Comparative Example #E7
Comparative Example #E7 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #E2 except for that polydimethylsiloxane (Mw=45,000, n=1.43)
was used instead of Bonding Agent Composition #E1.
Comparative Example #E8
Comparative Example #E8 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #E1 except for that polyvinylidenefluoride (Mw=120,000, n=1.42)
was used instead of Bonding Agent Composition #E1.
Comparative Example #E9
Comparative Example #E9 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #E1 except for that polyethylene film containing a filler (with
a visible transmission factor of 20% or less) was used for the transparent
plastic film.
Comparative Example #E10
Comparative Example #E10 consisted of electromagnetic shielding material
which was prepared identically as the electromagnetic shielding material
of Example #E2 except for that two layers of Electromagnetic Shielding
Film #E2 were bonded to each other (without the PET film carrying the
bonding agent on the other side).
The EMI shielding performance, visible light transmission factor,
warp-resistance, invisibility, and bonding property before and after
heating of the thus obtained electromagnetic shielding material were
actually measured, and the measured results are summarized in Tables 9 and
10.
The EMI shielding performance was measured by placing the specimen between
two flanges of a coaxial waveguide converter (marketed by Nihon Koshuha KK
under the tradename of TWC-S-024), and using a spectro-analyzer (marketed
by YHP under the tradename of 8510B Vector Network Analyzer) at the
frequency of 1 GHz.
The visible light transmission factor was measured as an average value of
transmission factor over the wavelength range of 400 to 800 nm by using a
double beam spectro-photoanalyzer (marketed by KK Hitachi under the
tradename of Type 200-10).
The invisibility was measured by placing the display device at the distance
of 0.5 m, and evaluating if the geometric pattern of the electroconductive
metallic material is visible or not. The specimens were graded into "very
good", and "good" depending on the degree of invisibility.
The bonding property was measured by using a tensile strength testing
machine (marketed by Toyo Baldwin KK under the tradename of Tensilon
UTM-4-100) with the width of 10 mm, 90 degree direction and peeling speed
of 50 mm/minute.
The refraction index was measured by using a refraction meter (marketed by
KK Atago Kogaku Kikai Seisakusho under the tradename of Abbe refraction
meter) at the temperature of 25.degree. C.
The warping of the electromagnetic shielding material was measured by
preparing a speciment of 650 mm by 100 mm, and measuring the amount of
warping along the lengthwise direction of the speciment.
The haziness was measured by using a haze meter (marketed by Nihon Densyoku
Kogyo KK under the tradename of COH-300A).
The reflective index was measured by using a spectro-chromatic meter
(marketed by Minolta KK under the tradename of CM-508d).
TABLE 9
Examples
items #E1 #E2 #E3 #E4 #E5 #E6 #E7 #E8
method for forming foil foil drawing foil foil foil
foil foil
conductive layer bonding bonding bonding bonding
bonding bonding bonding
conductive material Cu Cu Ni Cu Cu Cu
Cu Cu
bonding agent *1 SAF LE-0200 -- SAF SAF LE-0200
SAF LE-0200
bonding agent covering -- -- 3 -- -- 3 --
conductive pattern
shape square square square square square
square square square
patterning method *2 CE CE M CE CE CE
CE CE
line width (.mu.m) 20 15 10 20 12 15
20 15
line spacing (.mu.m) 1000 2000 1000 1000 1000 500
5000 2000
line thickness (.mu.m) 12 12 3 12 12 12
12 18
surface processing A A B A A A
A A
plastic film *4 PET PET PET PET PET PET
PET PET
bonding agent 1 2 1 3 1 2
3 2
composition *5
EMI shield 50 40 48 56 38 30
55 56
visible light 75 70 72 70 78 80
73 70
transmission factor
(%)
invisibility good good good good good good
good good
infrared blocking ratio -- -- -- -- -- -- -- --
(%)
haziness (%) 3.5 3.3 3.5 3.7 3.3 3.2
3.3 3.5
reflective index (%) 5.2 5.3 5.1 4.9 5 5
5.2 5.5
initial bonding force 1.2 1.7 1.2 1.8 1.5 1.6
1.2 1.7
(kgf/cm.sup.2)
bonding force after 80.degree. C.- 1.2 1.5 1.2 1.6
1.2 1.2 1.2 1.5
1,000 hours of aging
warping (mm) none none none none none none
none none
Examples
items #9 #10 #11 #12 #13 #14 #15 #16
method for forming foil foil foil drawing foil foil
foil foil
conductive layer bonding bonding bonding bonding
bonding bonding bonding
conductive material darkened Cu Cu Ni Cu Cu
Cu Cu
cu
bonding agent *1 SAF SAF LF-0200 -- SAF SAF
SAF SAF
bonding agent covering -- -- -- -- -- -- -- --
conductive pattern
shape square right right octagon + square
square square square
triangle hexagon square
patterning method *2 CE CE CE M CE CE
CE CE
line width (.mu.m) 20 20 15 10 20 20
20 20
line spacing (.mu.m) 1000 1000 2000 1000 1000 1000
1000 1000
line thickness (.mu.m) 12 12 12 3 12 12
12 12
surface processing A A A B A A
A A
plastic film *4 PET PET PET PET PS PET
PET PET
bonding agent #1 #1 #2 #1 #1 Infra #1 Infra #2 Infra
#3
composition *5
EMI shield 48 54 50 48 56 48
54 50
visible light 72 70 70 70 70 70
70 70
transmission factor
(%)
invisibility good good good good good good
good good
infrared blocking ratio -- -- -- -- -- 90 90 98
(%)
haziness (%) 3.5 3.3 3.3 3.6 3.5 3.7
3.7 3.7
reflective index (%) 5.3 5.1 4.8 4.8 4.5 5
5 5
initial bonding force 1.6 1.2 1.3 1.1 1.7 1.6
1.2 1.2
(kgf/cm.sup.2)
bonding force after 80.degree. C.- 1.4 1 1.1 1.1
1.5 1.3 1.2 1.2
1,000 hours of aging none none none none none none
none none
warping (mm)
*1 SAF: Nikaflex SAF, LF-0200: Pyralux LF-0200
*2 CE: chemical deposition, M: plating
*3 A: Surface Processed PET Film #1, B: Surface Processed PET Film #2
*4 PET: 50 .mu.m PET film, PS: 50 .mu.m PS film.
*5 #1: Bonding Agent Composition #1, #2: Bonding Agent Composition #2, and
#3: Bonding Agent Composition #3.
Infra #1: Infrared Blocking Layer Composition #1, Infra #2: Infrared
Blocking Layer Composition #2, Infra #3: Infrared Blocking Layer
Composition #3
TABLE 10
Comparative Examples
items #E1 #E2 #E3 #E4 #E5 #E6 #E7 #E8 #E9 #E10
method for forming vapor vapor foil foil foil foil
foil foil foil foil
conductive layer deposition deposition bonding bonding bonding
bonding bonding bonding bonding bonding
conductive material ITO Al Cu Cu Cu Cu
Cu Cu Cu Cu
bonding agent *1 -- -- SAF LF-0200 LF-0200 SAF SAF
SAF SAF LE-0200
bonding agent covering -- -- -- #E3 -- -- -- -- -- --
conductive pattern
shape uniform uniform square square square
square square square square square
patterning method *2 vapor vapor CE CE CE CE
CE CE CE CE
deposition deposition
line width (.mu.m) -- -- 50 15 15 20 20
20 20 15
line spacing (.mu.m) -- -- 1000 250 2000 1000 1000
1000 1000 2000
line thickness (.mu.m) -- -- 12 12 70 12 12
12 12 12
surface processing A A A A A A
A A A A
plastic film *4 PET PET PET PET PET PET
PET PET PE with --
filler
bonding agent #E1 #E2 #E1 #E2 #E2 Bond Bond Bond
#E1 --
composition *5 #E1
#E2 #E3
EMI shield 18 35 39 37 55 50
30 48 50 --
visible light 80 20> 55 40 60 20> 20>
20> 20> 20>
transmission factor
(%)
invisibility good NG NG NG NG NG
-- -- -- --
infrared blocking ratio 10 -- -- -- -- -- -- -- -- --
(%)
haziness (%) 3.2 3.2 3 3.8 3.7 15.8
10.2 13.5 18.8 --
reflective index (%) 4.8 4.8 5.3 4.6 4.8 10
8.8 10.6 15.6 --
initial bonding force 1.2 1.2 1.2 1.2 1.7 1.6
1.1 1.5 1.1 --
(kgf/cm.sup.2)
bonding force after 80.degree. C.- 1.2 1.2 1.2 0.8
1.2 1.2 0.8 1.1 0.9 --
1,000 hours of aging
warping (mm) none none none none none none
none none none 20
*1 SAF: Nikaflex SAF, LF-0200: Pyralux LF-0200
*2 CE: chemical deposition, M: plating
*3 A: Surface Processed PET Film #E1, B: Surface Processed PET Film #E2
*4 PET: 50 .mu.m PET film, PS: 50 .mu.m PS film.
*5 #E1: Bonding Agent Composition #E1, #E2: Bonding Agent Composition #E2,
and #E3: Bonding Agent Composition #E3.
Bond #E1: phenol-formaldehyde resin (n = 1.73), Bond #E2:
polydimethylsiloxane (n = 1.43), and Bond #E3: polyvinylidienefluoride (n
= 1.42)
Comparative Examples #E1 and #E2 used vapor deposited ITO and Al,
respectively, as the electroconductive material, and lacks favorable
electromagnetic shielding property. Comparative Example #E3 lacked a
favorable visible light transmission factor and invisibility because the
line width was 50 .mu.m which is substantially larger than the upper limit
of 25 .mu.m which is required by the present invention. Similarly as
Comparative Example #E3, Comparative Example #E4 lacked a favorable
visible light transmission factor and invisibility because the line
spacing was 250 .mu.m which is substantially narrower than the lower limit
of 500 .mu.m which is required by the present invention. Comparative
Example #E5 lacked a favorable invisibility because the line thickness was
70 .mu.m which is substantially larger than the upper limit of 18 .mu.m
which is required by the present invention. Comparative Example #E9 had a
poor visible light transmission factor of 20% or less because fairly
opaque polyethylene film containing a filler (having a visible light
transmission factor of 20% or less) was used instead of the transparent
plastic film. Comparative Example #E10 has an undesired tendency to warp
because the transparent plastic film was attached only to one side of the
transparent plastic base sheet instead of attaching a pair of transparent
plastic base sheet onto either side of the transparent plastic film each
via a bonding agent layer. On the other hand, the present invention
consists of electromagnetic shielding material, comprising a transparent
plastic base sheet, and transparent plastic film layers attached to either
side of the base sheet each via a bonding agent layer, one of the
transparent plastic film layers carrying a geometrically patterned
electroconductive material featuring a line width of 25 .mu.m or less, a
line spacing of 500 .mu.m or more, and a line thickness of 18 .mu.m or
less. The electromagnetic shielding material of Examples #E1 to #E16
according to the present invention has a favorable electromagnetic
shielding performance of 30 dB or more. According to the present
invention, the visible transmission factor is 70% or better, and a
favorable invisibility can be achieved. The values of haziness and
reflective index are favorably low. Also, the initial bonding force is
large and the bonding force drops very little even after 1,000 hours of
aging test at 80.degree. C. Also, the electromagnetic shielding material
according to the present invention does not tend to warp. According to
Examples #E14 to 16 which include an infrared blocking layer, the infrared
blocking ratio is favorably 90% or more.
As can be appreciated from the description of the examples, the
electromagnetic shielding material according to the present invention has
a high electromagnetic shielding property, free from leakage of
electromagnetic radiation, and favorable optical properties in terms of
visible light transmission factor, invisibility, and absence of
distortion. It also is free from warping, ad involves very little change
in the optical properties at high temperatures over an extended period of
time. Because the bonding film can be bonded onto the two sides of the
transparent base sheet by using a roll laminator, the electromagnetic
shielding material provided by the present invention allows a high
productivity to be achieved. The electromagnetic shielding material may be
given with an anti-reflection or anti-glare property by the anti-glare
process or the anti-reflection process. The electromagnetic shielding
material of the present invention may have an infrared blocking ratio of
90% or higher in the wavelength range of 900 to 1,100 nm by adding the
infrared absorbing agent. A continuous production can be made possible by
laminating the transparent plastic film over the transparent plastic base
sheet by the roll laminating method. By using polyethylene-terephthalate
film for the transparent plastic film, a highly transparent,
heat-resistant, economical and easy handling electromagnetic shielding
material can be obtained.
By using a layer of copper, aluminum or nickel having a thickness of 3 to
18 .mu.m for the electroconductive material layer, a highly workable and
economical electromagnetic shielding material which additionally provides
a wide viewing angle can be obtained. By using copper having at least its
outer surface darkened, a fade-resistant and high-contrast electromagnetic
shielding material can be obtained. By geometrically patterning the
electroconductive material over the transparent plastic base member with a
chemical etching process, a highly workable electromagnetic shielding
material can be obtained.
By using PMMA for the transparent plastic base sheet, a highly transparent
and workable electromagnetic shielding material can be obtained.
By selecting the materials such that the difference in refraction index
between the bonding layer and the transparent plastic base sheet (or the
transparent plastic film or, in case the assembly attached to transparent
plastic material, the bonding agent used for that purpose) is 0.14 or
less, a highly transparent electromagnetic shielding material can be
obtained.
When this electromagnetic shielding material is applied to a display
device, a high EMI shielding effect can be obtained, and it becomes
possible to allow the display device to be viewed comfortably with a high
visible light transmission factor and a favorable invisibility, free from
any haziness or reflection. Also, because the infrared radiation which may
be emitted from the display device is effectively shut off, any faulty
operation of equipment using remote controls can be avoided.
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